Methods of treating pediatric patients using dexmedetomidine

ABSTRACT

The presently disclosed subject matter relates to methods of administering an effective amount of dexmedetomidine to a pediatric patient in order to reduce the incidence of neurological damage. More particularly, the presently disclosed subject matter relates to methods of providing sedation or analgesia to a pediatric patient by administering a dexmedetomidine infusion and optionally a loading dose. The dexmedetomidine can be administered before, during, or after surgery.

1. CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/343,693 filed Jan. 4, 2012, which claims priority under 35 U.S.C. §119 to U.S. Provisional Application Ser. No. 61/547,626 filed Oct. 14,2011, both of which are hereby incorporated by reference in theirentireties, and to both of which priority is claimed.

2. FIELD OF THE INVENTION

The presently disclosed subject matter relates to a method of providinga safe and effective sedative and/or analgesic agent for pediatricpatients. More particularly, the presently disclosed subject matterrelates to reducing, preventing, and/or ameliorating neurological damagein a pediatric patient by administering dexmedetomidine.

3. BACKGROUND OF THE INVENTION

Sedation is an important component of care for pediatric patients in theintensive care unit (ICU) not only for their physiologic well being, butalso for patient safety and the safety of the caregivers.

Benzodiazepines and opioids, such as fentanyl or morphine, arefrequently administered to provide sedation and analgesia in thepediatric intensive care unit (PICU). Propofol has been shown to causesevere, life-threatening metabolic alterations in children includingcirculatory failure, and is not indicated in the pediatric populationfor continuous intensive care sedation. (See Propofol InjectableEmulsion [package insert]. Lake Forest Ill.: Hospira, Inc.: 2008). Withprolonged administration of benzodiazepines and opioids, tolerance andphysical dependence may develop. Midazolam sedation in some pediatricpatients causes oversedation alternating with under sedation andparadoxical agitation. (See Midazolam hydrochloride [Package Insert].Lake Forest, Ill.: Hospira, Inc.: 2005).

Recent reports of apoptosis and neurodevelopment abnormalities inneonatal and infant animal models from gamma-amino butyric acid(GABA)-agonist drugs have heightened the concern of sedating neonatesand infants with benzodiazepines. (See Young et al. Brit J Pharma 2005;146:189-197; and Sander et al. Brit J Anaesth 2008; 101 (5): 597-609).The concomitant administration of opioids further complicates pediatricpatient management because of respiratory depression. Therefore, thereis a significant unmet need for safe and effective sedation andanalgesia in pediatric patients.

Dexmedetomidine (Precedex®) is a highly selective alpha-2 adrenergicagonist with significant sedative, analgesic, and anxiolytic effects.Dexmedetomidine is currently approved by the FDA for sedation ofinitially intubated and mechanically ventilated adult patients in anintensive care setting, and is also approved for sedation ofnon-intubated adult patients as a component of monitored anesthesia careduring surgical or diagnostic procedures. Dexmedetomidine is the onlysedative approved in the United States for administration as acontinuous infusion in non-intubated ICU patients because it does notsignificantly affect respiratory drive.

Sedation with dexmedetomidine for adult patients in the ICU has beenwidely studied. When used in combination with opioids orbenzodiazepines, dexmedetomidine often allows for a reduction in thedoses of the other agents, reducing the risk of respiratory depression.

4. SUMMARY OF THE INVENTION

The present invention is directed to methods of sedation or analgesia ina pediatric patient in need thereof comprising administeringdexmedetomidine to the patient, wherein the dexmedetomidine isadministered in an amount effective to reduce the incidence ofneurological damage.

In one embodiment, the dexmedetomidine is administered at aconcentration of between about 0.01 to about 2.5 μg/kg/hr, the pediatricis about 17 years of age or younger, the dexmedetomidine is administeredas a continuous infusion for a period of time of less than about 36hours, and the dexmedetomidine is administered in an amount effective toreduce the incidence of neurological damage.

In a particular embodiment, the pediatric patient is a preterm neonate.In one embodiment, the pediatric patient's gestational age ranges fromabout 7 months to about 11 months.

In certain embodiments, the pediatric patient is intubated prior to,during, or after administration of the dexmedetomidine. In oneembodiment, the pediatric patient is critically ill.

In particular embodiments, the dexmedetomidine is parenterallyadministered. In certain embodiments, the dexmedetomidine isadministered by an intravenous infusion.

In particular embodiments, the neurological damage is cellulardegeneration or neuroapoptosis. In one embodiment, the neurologicaldamage occurs in a cortex lamina layer selected from the groupconsisting of layer I and layer II.

In certain embodiments, the dexmedetomidine is administered beforesurgery. In particular embodiments, the dexmedetomidine is administeredafter surgery. In a specific embodiment, the dexmedetomidine isadministered after cardiopulmonary bypass. In one embodiment, thepediatric patient has an age selected from the group consisting ofbetween about 12 to about 17 years of age and about 2 years of age oryounger.

In particular embodiments, the administration of dexmedetomidine reducesa need for rescue medication. In one embodiment, the rescue medicationis a sedative. In a specific embodiment, the rescue medication is ananalgesic.

In certain embodiments, the administration of dexmedetomidine furthercomprises a first loading dose prior to a maintenance dose and whereinthe loading dose ranges from about 0 to about 0.4 μg/kg. In oneembodiment, no loading dose is administered.

5. DESCRIPTION OF THE FIGURES

FIG. 1 depicts the mean plasma concentration of dexmedetomidine overtime for the full evaluable population in Example 3.

FIG. 2 depicts the plasma clearance over age for the full evaluablepopulation in Example 3.

FIG. 3 depicts the plasma clearance over weight for the full evaluablepopulation in Example 3.

FIG. 4 depicts the weight-adjusted plasma clearance versus age for thefull evaluable population in Example 3.

FIG. 5 depicts the weight-adjusted volume of distribution versus age forthe full evaluable population in Example 3.

FIG. 6 depicts the predicted mean curves for AUC_(0-∞) generated usingthe power fit model for Example 3.

FIG. 7 depicts the predicted mean curves for AUC_(0-t) generated usingthe power fit model for Example 3.

FIG. 8 depicts the predicted mean curves for C_(max) generated using thepower fit model for Example 3.

FIG. 9 depicts the predicted mean curves for C_(ss) generated using thepower fit model for Example 3.

FIG. 10 depicts the average Ramsay Sedation Score (RSS) versus AUC_(0-∞)for the full evaluable population.

FIG. 11 depicts the average Ramsay Sedation Score (RSS) versus C_(ss)for the full evaluable population.

FIG. 12 depicts representative photomicrographs of TUNEL staining of thefrontal cortex of neonatal monkeys at 5× and 10× magnification.

FIG. 13 depicts representative photomicrographs of activated caspase 3staining of the frontal cortex of neonatal monkeys at 5× and 10×magnification.

FIG. 14 depicts representative photomicrographs of activated caspase 3staining of the frontal cortex of neonatal monkeys at 20× magnification.

FIG. 15 depicts representative photomicrographs of the silver stainingof the frontal cortex of neonatal monkeys at 20× magnification.

FIGS. 16A-C depict lineplots of plasma dexmedetomidine concentrationsversus time since the start of the loading dose infusion for eachtreatment group for the treatment groups in the studies of Examples 1,3, and 5.

FIGS. 17A-C depicts lineplots of dexmedetomidine concentrations versustime since the end of the maintenance infusion are shown for eachtreatment group for the treatment groups in the studies of Examples 1,3, and 5.

FIGS. 18A-B depict a semilogarithmic scatterplot of dose-normalizeddexmedetomidine plasma concentrations versus time since the end of themaintenance infusion for the studies of Examples 1, 3, and 5.

FIGS. 19A-B depict goodness-of-fit plots for the individual predicteddexmedetomidine Cp base structural model for the pooled dataset ofExamples 1, 3, and 5.

FIG. 20 depicts the 90% prediction interval, derived from the 1000simulated datasets, overlaid on the observed dexmedetomidineconcentrations versus time since the end of the maintenance infusion ofExamples 1, 3, and 5.

FIG. 21 depicts a comparison of the 5th, 50th, and 95th percentile ofthe prediction-corrected observed and model-based simulated data ofExamples 1, 3, and 5.

FIGS. 22A-D depicts goodness-of-fit plots for the final populationpharmacokinetics model for the entire population for the data ofExamples 1, 3, and 5.

FIG. 23 in the upper panel depicts the geometric means and 95%confidence intervals for the individual Bayesian estimates ofdexmedetomidine clearance plotted at the midpoint of each age group. Thelower panels depict the corresponding weight-adjusted estimates fordexmedetomidine clearance. A line for the population model-based typicalvalue of each parameter versus age is overlaid in each plot.

FIG. 24 in the upper panel depicts the geometric means and 95%confidence intervals for the individual Bayesian estimates ofdexmedetomidine volume of distribution plotted at the midpoint of eachage group. The lower panels depict the corresponding weight-adjustedestimates for dexmedetomidine volume of distribution. A line for thepopulation model-based typical value of each parameter versus age isoverlaid in each plot.

FIG. 25 depicts the pairwise scatterplots of interindividual varianceterms from the final model in Example 6.

FIG. 26 depicts the 95% confidence intervals for the individual Bayesianestimates expressed as the percent of the geometric mean ofdexmedetomidine weight-adjusted CL for each age group as determined fromthe analysis performed in Example 6.

FIG. 27 depicts the 95% confidence intervals for the individual Bayesianestimates expressed as the percent of the geometric mean ofdexmedetomidine weight-adjusted volume of distribution for each agegroup as determined from the analysis performed in Example 6.

FIG. 28 depicts the 95% confidence intervals for the individual Bayesianestimates expressed as the percent of the geometric mean ofdexmedetomidine weight-adjusted CL for each age group as determined fromthe analysis performed in Example 8.

FIG. 29 depicts the 95% confidence intervals for the individual Bayesianestimates expressed as the percent of the geometric mean ofdexmedetomidine weight-adjusted volume of distribution for each agegroup as determined from the analysis performed in Example 8.

FIGS. 30A-H depict the goodness-of-fit plots for the final populationpharmacokinetic model for dexmedetomidine of Example 8.

FIGS. 31A-B depict the prediction-corrected visual predictive checkresults for the dexmedetomidine concentration versus time since end ofIV.

FIG. 32 depicts the geometric means and 95% confidence intervals for theBayesian estimates of dexmedetomidine clearance and weight-adjustedclearance in specified age groups with the population model-basedtypical values of clearance and weight-adjusted clearance overlaid.

FIG. 33 depicts the geometric means and 95% confidence intervals for theBayesian estimates of dexmedetomidine volume distribution andweight-adjusted volume of distribution in specified age groups, with thepopulation model-based typical values of volume of distribution andweight-adjusted volume of distribution overlaid.

FIGS. 34A-C depict the predicted mean curve for AUC_(0-inf), AUC_(0-t),and C_(max) generated using the power fit model.

FIG. 35 depicts a linear plot illustrating the mean dexmedetomidineconcentrations over time. Time Point: 1=pre-dose, 2=end of bolus, 3=30minutes after start of infusion, 4=60 minutes after start of infusion,5=2 hours after start of infusion, 6=4 to 6 hours after start ofinfusion, 7=6 hours after start of infusion, 8=12 hours after start ofinfusion, 8.1=23 hours after start of infusion, 9=30 to 15 minutes priorto end of infusion, 10=end of infusion, 11=15 minutes after end ofinfusion, 12=30 minutes after end of infusion, 13=60 minutes after endof infusion, 14=2 hours after end of infusion, 15=4 hours after end ofinfusion, 16=8 hours after end of infusion, 17=12 hours after end ofinfusion, 18=15 to 18 hours after end of infusion, 19=24 hours after endof infusion.

FIGS. 36A-B depict the clearance and weight-adjusted clearance over age.

6. DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to methods of sedation or analgesia ina pediatric patient in need thereof comprising administration ofdexmedetomidine to the patient, wherein the dexmedetomidine isadministered in an amount effective to reduce the incidence ofneurological damage.

For clarity and not by way of limitation, this detailed description isdivided into the following sub-portions:

6.1 Definitions;

6.2 Pharmaceutical formulations;

6.3 Patient populations; and

6.4 Methods of treatment.

6.1 Definitions

The terms used in this specification generally have their ordinarymeanings in the art, within the context of this invention and in thespecific context where each term is used. Certain terms are discussedbelow, or elsewhere in the specification, to provide additional guidanceto the practitioner in describing the compositions and methods of theinvention and how to make and use them.

According to the present invention, the term “dexmedetomidine” as usedherein refers to a substantially pure, optically active dextrorotarystereoisomer of medetomidine, as the free base or pharmaceuticallyacceptable salt. In one, non-limiting embodiment, dexmedetomidine hasthe formula (S)-4-[1-(2,3-dimethylphenyl)ethyl]-3H-imidazole. Apharmaceutically acceptable salt of dexmedetomidine can includeinorganic acids such as hydrochloric acid, hydrobromic acid, sulfuricacid, nitric acid, phosphoric acid and the like, and organic acids suchas acetic acid, propionic acid, glycolic acid, pyruvic acid, oxalicacid, malic acid, malonic acid, succinic acid, maleic acid, fumaricacid, tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelicacid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid,and salicylic acid. Preferably, the dexmedetomidine salt isdexmedetomidine HCl. In other non-limiting embodiments, dexmedetomidinecomprises the structure depicted below in Formula I

The term “pharmaceutical composition” as used in accordance with thepresent invention relates to compositions that can be formulated in anyconventional manner using one or more pharmaceutically acceptablecarriers or excipients. A “pharmaceutically acceptable” carrier orexcipient, as used herein, means approved by a regulatory agency of theFederal or a state government, or as listed in the U.S. Pharmacopoeia orother generally recognized pharmacopoeia for use in mammals, and moreparticularly in humans.

The term “dosage” is intended to encompass a formulation expressed interms of μg/kg/hr, μg/kg/day, mg/kg/day, or mg/kg/hr. The dosage is theamount of an ingredient administered in accordance with a particulardosage regimen. A “dose” is an amount of an agent administered to amammal in a unit volume or mass, e.g., an absolute unit dose expressedin mg of the agent. The dose depends on the concentration of the agentin the formulation, e.g., in moles per liter (M), mass per volume (m/v),or mass per mass (m/m). The two terms are closely related, as aparticular dosage results from the regimen of administration of a doseor doses of the formulation. The particular meaning in any case will beapparent from context.

The terms “therapeutically effective dose,” “effective amount,” and“therapeutically effective amount” refer to the amount sufficient toproduce the desired effect. In some non-limiting embodiments, a“therapeutically effective dose” means an amount sufficient to reduce byat least about 15%, preferably by at least 50%, more preferably by atleast 90%, and most preferably prevent, a clinically significant deficitin the activity, function and response of the host. Alternatively, atherapeutically effective amount is sufficient to cause an improvementin a clinically significant condition in the host. These parameters willdepend on the severity of the condition being treated, other actions,such as diet modification, that are implemented, the weight, age, andsex of the subject, and other criteria, which can be readily determinedaccording to standard good medical practice by those of skill in theart. In other non-limiting embodiments a therapeutic response may be anyresponse that a user (e.g., a clinician) will recognize as an effectiveresponse to the therapy. Thus, a therapeutic response will generally bean induction of a desired effect, such as, for example, sedation oranalgesia.

The terms “intensive care unit” or “ICU” as used herein refer to anysetting that provides intensive care.

The term “gestational age” as used herein is calculated as the timeelapsed since the first day of the last menstrual period. If pregnancywas achieved using assisted reproductive technology, gestational age iscalculated by adding two weeks to the gestational age as calculatedabove.

The term “pediatric patient” as used herein means a human patient thatis 17 years old or younger. In certain non-limiting embodiments, thepatient is 16 years old or younger, or 15 years old or younger, or 14years old or younger, or 13 years old or younger, or 12 years old oryounger, or 11 years old or younger, or 10 years old or younger, or 9years old or younger, or 8 years old or younger, or 7 years old oryounger, or 6 years old or younger, or 5 years old or younger, or 4years old or younger, or 3 years old or younger, or 2 years old oryounger, or 1 year old or younger, or 6 months old or younger, or 4months old or younger, or 2 months old or younger, or 1 months old oryounger. In particular embodiments, the pediatric patient is betweenabout 12 to about 17 years of age. In one embodiment, the pediatricpatient has an age selected from the group consisting of between about12 to about 17 years of age and about 2 years of age or younger. In oneembodiment, the pediatric patient has exited the womb just prior toadministration of the dexmedetomidine.

In certain embodiments, the “pediatric patient” is a preterm neonate. Asused herein, the term “preterm neonate” refers to a child that is bornprior to 37 weeks from the start of the last menstrual period. Ifpregnancy was achieved using assisted reproductive technology, a childis a preterm neonate if the child is calculated by adding two weeks tothe age as calculated above.

In certain embodiments, the pediatric patient has a gestational age ofbetween about 20 weeks and about 44 weeks, or between about 20 weeks andabout 40 weeks, or between about 20 weeks and about 38 weeks, or betweenabout 20 weeks and about 36 weeks, or between about 20 weeks and about34 weeks, or between about 20 weeks and about 30 weeks, or between about20 weeks and about 28 weeks, or between about 20 weeks and about 24weeks. In certain embodiments, the pediatric patient has a gestationalage of between about 36 weeks and about 44 weeks, or between about 36weeks and about 42 weeks, or between about 36 weeks and about 40 weeks,or between about 36 weeks and about 38 weeks.

As used herein, the term “neurological damage” refers to various typesof neurocognitive, psychocognitive, and/or neuromotor or motorimpairment, or combinations thereof, discussed in further detail below.

As used herein, the term “a reduction in the incidence of” refers to areduction in the severity of, reduction in the number of, prevention of,or delay of the development of one or more incidences thereof, or acombination thereof.

The term “about” or “approximately” means within an acceptable errorrange for the particular value as determined by one of ordinary skill inthe art, which will depend in part on how the value is measured ordetermined, i.e., the limitations of the measurement system. Forexample, “about” can mean within 3 or more than 3 standard deviations,per the practice in the art. Alternatively, “about” can mean a range ofup to 20%, preferably up to 10%, more preferably up to 5%, and morepreferably still up to 1% of a given value. Alternatively, particularlywith respect to biological systems or processes, the term can meanwithin an order of magnitude, preferably within 5-fold, and morepreferably within 2-fold, of a value.

6.2 Pharmaceutical Compositions

The pharmaceutical compositions of dexmedetomidine suitable forparenteral administration can be in the form of suspensions, solutions,or emulsions, in oily or aqueous vehicles, and can contain formulatoryagents such as suspending, stabilizing, solubilizing, and/or dispersingagents. The form can be sterile and can be fluid. It can be stable underthe conditions of manufacture and storage and can be preserved againstthe contaminating action of microorganisms such as bacteria and fungi.Alternatively, the dexmedetomidine can be in sterile powder form forreconstitution with a suitable vehicle before use. The pharmaceuticalcompositions can be presented in unit dose form, in ampoules, or otherunit-dose containers, or in multi-dose containers. Alternatively, thepharmaceutical compositions can be stored in a freeze-dried(lyophilized) condition requiring only the addition of sterile liquidcarrier, for example, water for injections immediately prior to use.Extemporaneous injection solutions and suspensions can be prepared fromsterile powders, granules or tablets.

In some non-limiting embodiments, the dexmedetomidine composition isformulated as a liquid. In certain non-limiting embodiments, thedexmedetomidine liquid composition comprises dexmedetomidine, or apharmaceutically acceptable salt thereof, at a concentration of betweenabout 0.005 μg/mL and about 100 μg/mL, or between about 0.005 μg/mL andabout 50 μg/mL, or between about 0.005 μg/mL and about 25 μg/mL, orbetween about 0.005 μg/mL and about 15 μg/mL, or between about 0.005μg/mL and about 10 μg/mL, or between about 0.005 μg/mL and about 7μg/mL, or between about 0.005 μg/mL and about 5 μg/mL, or between about0.005 μg/mL and about 4 μg/mL, or between about 0.005 μg/mL and about 3μg/mL, or between about 0.005 μg/mL and about 2 μg/mL, or between about0.005 μg/mL and about 1 μg/mL, or between about 0.005 μg/mL and about0.5 μg/mL, or between about 0.005 μg/mL and about 0.05 μg/mL.

In certain non-limiting embodiments, the dexmedetomidine liquidcomposition comprises dexmedetomidine, or a pharmaceutically acceptablesalt thereof, at a concentration of about 0.5 μg/mL, or about 1.0 μg/mL,or about 2.0 μg/mL, or about 4.0 μg/mL.

In one embodiment, the dexmedetomidine composition is a premixedformulation that does not require reconstitution or dilution prior toadministration to a patient, as disclosed in U.S. application Ser. No.13/343,672, filed on Jan. 4, 2012, titled “Dexmedetomidine PremixFormulation,” is hereby incorporated by reference in its entirety.

Excipients that are suitable for the dexmedetomidine composition includepreservatives, suspending agents, stabilizers, dyes, buffers,antibacterial agents, antifungal agents, and isotonic agents, forexample, sugars or sodium chloride. As used herein, the term“stabilizer” refers to a compound optionally used in the pharmaceuticalcompositions of the present invention in order to avoid the need forsulphite salts and increase storage life. Non-limiting examples ofstabilizers include antioxidants.

The pharmaceutical composition can comprise one or more pharmaceuticallyacceptable carriers. The carrier can be a solvent or dispersion medium.Non-limiting examples of pharmaceutically acceptable carriers includewater, saline, ethanol, polyol (e.g., glycerol, propylene glycol andliquid polyethylene glycol), oils, and suitable mixtures thereof.

The parenteral formulation can be sterilized. Non-limiting examples ofsterilization techniques include filtration through abacterial-retaining filter, terminal sterilization, incorporation ofsterilizing agents, irradiation, heating, vacuum drying, and freezedrying.

6.3 Patient Populations

The presently disclosed subject matter comprises administeringdexmedetomidine to a pediatric patient. In certain embodiments, thepediatric patient is intubated. The pediatric patient can be intubatedprior to, during, or after administration of the dexmedetomidine. Thepediatric patient can be intubated by the nasotracheal, endotracheal,direct oral laryngoscopy or by fibreoptic routes, or via tracheotomy.

In particular embodiments, the patient is critically ill. In oneembodiment, the pediatric patient suffers from one or more medicalconditions. In certain embodiments, the medical condition is a lungdisorder, brain disorder, heart disorder, liver disorder, kidneydisorder, eye or ear disorder, gastrointestinal disorder, or skindisorder. Non-limiting examples of lung disorders include respiratorydistress syndrome, pneumonia, bronchopulmonary dysplasia, apnea ofprematurity, and pneumothorax. Non-limiting examples of brain disordersinclude intraventricular hemorrhage and cerebral palsy. Non-limitingexamples of liver disorders include jaundice. Non-limiting examples ofheart disorders include cardiac ischemia and patent ductus arteriosus.Non-limiting examples of eye disorders include retinopathy ofprematurity, myopia, and strabismus. Non-limiting examples of othermedical conditions includes heroin withdrawal, cocaine withdrawal,alcohol fetal syndrome, HIV-positive status, and Tay Sachs disease.

In one embodiment, the patient has undergone surgery. The patient mayundergo surgery prior to, during, and/or after administration of thedexmedetomidine. In certain embodiments, the dexmedetomidine isadministered prior to surgery. In one embodiment, the dexmedetomidine isadministered prior to surgery for the purpose of reducing an incidenceof neurological damage. In some embodiments, the dexmedetomidine isadministered prior to and during surgery. In particular embodiments, thedexmedetomidine is administered prior to and after surgery. In certainembodiments, the dexmedetomidine is administered during and aftersurgery. In particular embodiments, the dexmedetomidine is administeredprior to, during, and after surgery.

Surgery refers to any manual or operative methods or manipulations forthe treatment or prevention of disease, injury or deformity. Surgery canbe performed by a doctor, surgeon or dentist, generally in a hospital orother health care facility. Pediatric patients undergoing surgery can behospitalized or ambulatory, e.g., out-patient surgery. The surgery canbe conservative (e.g. surgery to preserve or remove with minimal risk,diseased or injured organs, tissues, or extremities) or radical (e.g.surgery designed to extirpate all areas of locally extensive disease andadjacent zones of lymphatic drainage).

Non-limiting examples of surgery include surgeries performed on thecardiovascular system, including the heart and blood vessels; surgeriesperformed on the musculoskeletal system, including the bones andmuscles; surgeries performed on the respiratory system, including thetrachea and the lungs; surgeries performed on the integumentary system,including the skin and nails; surgeries performed on the mediastinum anddiaphragm; surgeries performed on the digestive system, including theesophagus, stomach, gall bladder and intestines; surgeries performed onthe urinary system, including the kidneys and bladder; surgeriesperformed on the male genital system; surgeries performed on the femalegenital system; surgeries performed on the endocrine system, includingthe pituitary gland, the adrenal glands, and the endocrine thyroidgland; surgeries performed on the nervous system, including the brain,spinal cord and peripheral nerves; surgeries performed on the eye andocular adnexa; and surgeries performed on the auditory system.

Non-limiting examples of surgeries performed on the cardiovascularsystem include the repair of congenital heart defects after birth andheart transplant surgery. Non-limiting examples of surgeries performedon the musculoskeletal system include fracture repair, scoliosis surgeryand tendon lengthening. Non-limiting examples of surgeries performed onthe respiratory system include lung transplants, thoracotomy andpneumothorax surgery. Non-limiting examples of surgeries performed onthe integumentary system include burn treatment and skin grafting.Non-limiting examples of surgeries performed on the mediastinum anddiaphragm include treatment of congenital diaphragmatic hernia andremoval of mediastinal cysts and tumors. Non-limiting examples ofsurgeries performed on the digestive system include intestinal resectionand treatment of pyloric stenosis. Non-limiting examples of surgeriesperformed on the urinary system may include kidney transplants, andtreatment of bladder divurticula. Non-limiting examples of surgeriesperformed on the male genital system may include treatment ofundescended testes. Non-limiting examples of surgeries performed on thefemale genital system may include ovarian cystectomy. Non-limitingexamples of surgeries performed on the endocrine system may includetreatment of hyperparathyroidism. Non-limiting examples of surgeriesperformed on the nervous system may include laminectomy and corpuscallosotomy. Non-limiting examples of surgeries performed on the eye mayinclude strabismus surgery. Non-limiting examples of surgeries performedon the auditory system include cochlear implantation. Additionalnon-limiting examples of surgery include tonsillectomy, cleft lip andpalate repair, treatment of lymphangioma, tracheoesophageal fistularepair, neuroblastoma surgery, and treatment of esophageal atresia. Inone embodiment, the patient has undergone cardiopulmonary bypass.

6.4 Methods of Treatment

As noted above, the methods of treatment of the invention are directedto methods of sedation or analgesia in a pediatric patient comprisingadministration of dexmedetomidine to the patient, wherein thedexmedetomidine is administered in an amount effective to reduceincidence of neurological damage.

The dexmedetomidine for use in the invention can be administered via anysuitable route, including parenteral, intravenous, and oral routes.Non-limiting examples of parenteral routes of administration includeintravenous, intramuscular, subcutaneous, intraperitoneal orintrathecal. Parenteral administration may be by periodic injections ofa bolus of the preparation, or may be administered by intravenous orintraperitoneal administration from a reservoir which is external (e.g.,an intravenous bag) or internal (e.g., a bioerodable implant, abioartificial organ). See, e.g., U.S. Pat. Nos. 4,407,957 and 5,798,113,each incorporated herein by reference in their entireties.Intrapulmonary delivery methods and apparatus are described, forexample, in U.S. Pat. Nos. 5,654,007, 5,780,014, and 5,814,607, eachincorporated herein by reference in their entireties. Other usefulparenteral delivery systems include ethylene-vinyl acetate copolymerparticles, osmotic pumps, implantable infusion systems, pump delivery,encapsulated cell delivery, liposomal delivery, needle-deliveredinjection, needle-less injection, nebulizer, aeorosolizer,electroporation, and transdermal patch. Needle-less injector devices aredescribed in U.S. Pat. Nos. 5,879,327; 5,520,639; 5,846,233 and5,704,911, the specifications of which are herein incorporated herein byreference in their entireties.

In yet another non-limiting embodiment, the therapeutic compound can bedelivered in a controlled or sustained release system. For example, acompound or composition may be administered using intravenous infusion,continuous infusion, an implantable osmotic pump, or other modes ofadministration. In one embodiment, a pump may be used (see Sefton, 1987,CRC Crit. Ref Biomed. Eng. 14:201; Buchwald et al., 1980, Surgery88:507; Saudek et al., 1989, N. Engl. J. Med. 321:574). In anotherembodiment, polymeric materials can be used (see Langer and Wise eds.,1974, Medical Applications of Controlled Release, CRC Press: Boca Raton,Fla.; Smolen and Ball eds., 1984, Controlled Drug Bioavailability, DrugProduct Design and Performance, Wiley, N.Y.; Ranger and Peppas, 1983, J.Macromol. Sci. Rev. Macromol. Chem., 23:61; Levy et al., 1985, Science228:190; During et al., 1989, Ann. Neurol., 25:351; Howard et al., 9189,J. Neurosurg. 71:105). In yet another embodiment, a controlled releasesystem can be placed in proximity of the therapeutic target, i.e., thebrain, thus requiring only a fraction of the systemic dose (see, e.g.,Goodson, 1984, in Medical Applications of Controlled Release, Vol. 2,pp. 115-138).

In certain embodiments, the dexmedetomidine is administered as acontinuous intravenous dose to a pediatric patient at a concentration ofbetween about 0.005 μg/kg/hr and about 50 μg/kg/hr, or between about0.005 μg/kg/hr and about 25 μg/kg/hr, or between about 0.005 μg/kg/hrand about 15 μg/kg/hr, or between about 0.005 μg/kg/hr and about 5μg/kg/hr, or between about 0.005 μg/kg/hr and about 2 μg/kg/hr, orbetween about 0.005 μg/kg/hr and about 1.5 μg/kg/hr, or between about0.005 μg/kg/hr and about 1 μg/kg/hr, or between about 0.005 μg/kg/hr andabout 0.5 μg/kg/hr, or between about 0.005 μg/kg/hr and about 0.25μg/kg/hr. In preferred non-limiting embodiments, the concentration isbetween about 0.025 μg/kg/hr and about 2.0 μg/kg/hr. In particularembodiments, the dexmedetomidine is administered as a continuousintravenous dose to a pediatric patient at a concentration of betweenabout 0.005 μg/kg/hr and about 50 μg/kg/hr, or between about 0.025μg/kg/hr and about 50 μg/kg/hr, or between about 0.05 μg/kg/hr and about50 μg/kg/hr, or between about 0.01 μg/kg/hr and about 50 μg/kg/hr, orbetween about 0.2 μg/kg/hr and about 50 μg/kg/hr, or between about 0.25μg/kg/hr and about 50 μg/kg/hr, or between about 0.5 μg/kg/hr and about50 μg/kg/hr, or between about 0.7 μg/kg/hr and about 50 μg/kg/hr, orbetween about 1.0 μg/kg/hr and about 50 μg/kg/hr, or between about 1.5μg/kg/hr and about 50 μg/kg/hr, or between about 2.0 μg/kg/hr and about50 μg/kg/hr, or between about 5.0 μg/kg/hr and about 50 μg/kg/hr, orbetween about 10 μg/kg/hr and about 50 μg/kg/hr, or between about 20μg/kg/hr and about 50 μg/kg/hr.

In particular embodiments, the dexmedetomidine is administered as acontinuous intravenous dose to a pediatric patient at a concentration ofabout 0.01 μg/kg/hr, or about 0.025 μg/kg/hr, or about 0.05 μg/kg/hr, orabout 0.1 μg/kg/hr, or about 0.2 μg/kg/hr, or about 0.25 μg/kg/hr, orabout 0.3 μg/kg/hr, or about 0.4 μg/kg/hr, or about 0.5 μg/kg/hr, orabout 0.6 μg/kg/hr, or about 0.7 μg/kg/hr, or about 0.75 μg/kg/hr, orabout 0.8 μg/kg/hr, or about 0.9 μg/kg/hr, or about 1.0 μg/kg/hr, orabout 1.1 μg/kg/hr, or about 1.2 μg/kg/hr, or about 1.3 μg/kg/hr, orabout 1.4 μg/kg/hr, or about 1.5 μg/kg/hr, or about 1.6 μg/kg/hr, orabout 1.7 μg/kg/hr, or about 1.8 μg/kg/hr, or about 1.9 μg/kg/hr, orabout 2.0 μg/kg/hr, or about 2.1 μg/kg/hr, or about 2.2 μg/kg/hr, orabout 2.3 μg/kg/hr, or about 2.4 μg/kg/hr, or about 2.5 μg/kg/hr. Incertain embodiments, the dexmedetomidine is administered as a continuousintravenous dose at a concentration of about 3.0 μg/kg/hr, or about 3.5μg/kg/hr, or about 4.0 μg/kg/hr, or about 4.5 μg/kg/hr, or about 4.0μg/kg/hr, or about 4.5 μg/kg/hr, or about 5.0 μg/kg/hr, or about 5.5μg/kg/hr, about 6.0 μg/kg/hr, or about 6.5 μg/kg/hr, or about 7.0μg/kg/hr, or about 7.5 μg/kg/hr, about 8.0 μg/kg/hr, or about 8.5μg/kg/hr, or about 9.0 μg/kg/hr, or about 9.5 μg/kg/hr, or about 10μg/kg/hr, or about 11 μg/kg/hr, or about 12 μg/kg/hr, or about 13μg/kg/hr, or about 14 μg/kg/hr, or about 15 μg/kg/hr, or about 16μg/kg/hr, or about 17 μg/kg/hr, or about 18 μg/kg/hr, or about 19μg/kg/hr, or about 20 μg/kg/hr, or about 21 μg/kg/hr, or about 22μg/kg/hr, or about 23 μg/kg/hr, or about 24 μg/kg/hr, or about 25μg/kg/hr, or about 27.5 μg/kg/hr, or about 30 μg/kg/hr, or about 32.5μg/kg/hr, or about 35 μg/kg/hr, or about 40 μg/kg/hr, or about 45μg/kg/hr, or about 50 μg/kg/hr.

In particular embodiments, the dexmedetomidine is administered as acontinuous intravenous dose for a period of time of between about 1 andabout 10 minutes, or between about 1 and about 20 minutes, or betweenabout 1 and about 30 minutes, or between about 1 and about 2 hours, orbetween about 1 and about 3 hours, or between about 1 and about 4 hours,or between about 1 and about 5 hours, or between about 1 and about 6hours, or between about 1 and about 7 hours, or between about 1 andabout 8 hours, or between about 1 and about 9 hours, or between about 1and about 10 hours, or between about 1 and about 11 hours, or betweenabout 1 and about 12 hours, or between about 1 and about 13 hours, orbetween about 1 and about 14 hours, or between about 1 and about 15hours, or between about 1 and about 16 hours, or between about 1 andabout 17 hours, or between about 1 and about 18 hours, or between about1 and about 19 hours, or between about 1 and about 20 hours, or betweenabout 1 and about 21 hours, or between about 1 and about 22 hours, orbetween about 1 and about 23 hours, or between about 1 and about 24hours. In preferred non-limiting embodiments, the dexmedetomidine isadministered as a continuous dose for a period of time of between about6 and about 24 hours. In certain embodiments, the dexmedetomidine isadministered as a continuous dose for a period of time of about 6 hours,or about 7 hours, or about 8 hours, or about 9 hours, or about 10 hours,or about 11 hours, or about 12 hours, or about 13 hours, or about 14hours, or about 15 hours, or about 16 hours, or about 17 hours, or about18 hours, or about 19 hours, or about 20 hours, or about 21 hours, orabout 22 hours, or about 23 hours, or about 24 hours.

In certain non-limiting embodiments, the administration ofdexmedetomidine comprises a first loading dose administered prior to asecond maintenance dose. When administered as a loading dose followed bya maintenance dose, the loading dose can be a dose of between about 0μg/kg and about 5 μg/kg, or between about 0.005 μg/kg and about 4.5μg/kg, or between about 0.005 μg/kg and about 3 μg/kg, or between about0.005 μg/kg and about 2.5 μg/kg, or between about 0.005 μg/kg and about2 μg/kg, or between about 0.005 μg/kg and about 1.5 μg/kg, or betweenabout 0.005 μg/kg and about 1 μg/kg, or between about 0.005 μg/kg andabout 0.5 μg/kg, or between about 0.005 μg/kg and about 0.25 μg/kg, orbetween about 0 μg/kg and about 0.4 μg/kg. In preferred non-limitingembodiments, the loading dose is between about 0 μg/kg and about 1.0μg/kg. In particular embodiments, the loading dose is about 0.01 μg/kg,or about 0.025 μg/kg, or about 0.05 μg/kg, or about 0.1 μg/kg, or about0.2 μg/kg, or about 0.25 μg/kg, or about 0.3 μg/kg, or about 0.35 μg/kg,or about 0.4 μg/kg, or about 0.5 μg/kg, or about 0.6 μg/kg, or about 0.7μg/kg, or about 0.8 μg/kg, or about 0.9 μg/kg, or about 1.0 μg/kg, orabout 1.1 μg/kg, or about 1.2 μg/kg, or about 1.3 μg/kg, or about 1.4μg/kg, or about 1.5 μg/kg, or about 1.6 μg/kg, or about 1.7 μg/kg, orabout 1.8 μg/kg, or about 1.9 μg/kg, or about 2.0 μg/kg, or about 2.1μg/kg, or about 2.2 μg/kg, or about 2.3 μg/kg, or about 2.4 μg/kg, orabout 2.5 μg/kg. In certain embodiments, the loading dose is about 3.0μg/kg, or about 3.5 μg/kg, or about 4.0 μg/kg, or about 4.5 μg/kg, orabout 4.0 μg/kg, or about 4.5 μg/kg, or about 5.0 μg/kg, or about 5.5μg/kg, about 6.0 μg/kg, or about 6.5 μg/kg, or about 7.0 μg/kg, or about7.5 μg/kg, about 8.0 μg/kg, or about 8.5 μg/kg, or about 9.0 μg/kg, orabout 9.5 μg/kg, or about 10 μg/kg, or about 11 μg/kg, or about 12μg/kg, or about 13 μg/kg, or about 14 μg/kg, or about 15 μg/kg, or about16 μg/kg, or about 17 μg/kg, or about 18 μg/kg, or about 19 μg/kg, orabout 20 μg/kg, or about 21 μg/kg, or about 22 μg/kg, or about 23 μg/kg,or about 24 μg/kg, or about 25 μg/kg, or about 27.5 μg/kg, or about 30μg/kg, or about 32.5 μg/kg, or about 35 μg/kg, or about 40 μg/kg, orabout 45 μg/kg, or about 50 μg/kg.

In certain embodiments, the loading dose is below about 0.5 μg/kg, orbelow about 0.45 μg/kg, or below about 0.4 μg/kg, or below about 0.35μg/kg, or below about 0.3 μg/kg, or below about 0.25 μg/kg, or belowabout 0.2 μg/kg, or below about 0.15 μg/kg, or below about 0.1 μg/kg, orbelow about 0.05 μg/kg, or below about 0.01 μg/kg. In particularembodiments, no loading dose is administered.

The loading dose can be administered for a period of time of betweenabout 1 and about 5 minutes, or between about 1 and about 10 minutes, orbetween about 1 and about 15 minutes, or between about 1 and about 20minutes, or between about 1 and about 25 minutes, or between about 1 andabout 30 minutes, or between about 1 and about 45 minutes, or betweenabout 1 and about 60 minutes. Following the loading dose, themaintenance dose can be administered for a period of time as describedabove for a single continuous dose. In preferred non-limitingembodiments, the loading dose is administered for a period of time ofabout 10 to about 20 minutes. In particular embodiments, the loadingdose is administered for a period of time of about 5 minutes, or about7.5 minutes, or about 10 minutes, or about 12.5 minutes, or about 15minutes, or about 20 minutes, or about 25 minutes, or about 30 minutes,or about 35 minutes, or about 40 minutes, about 45 minutes, or about 50minutes, or about 55 minutes, or about 60 minutes.

In certain non-limiting embodiments, the dexmedetomidine, whenadministered as a single continuous, loading or maintenance dose, isadministered for a period of time of about 1 hour to about 7 days, orabout 1 hour to about 4 days, or about 1 hour to about 48 hours, orabout 1 hour to about 36 hours, or about 1 hour to about 24 hours, orabout 1 hour to about 12 hours. In particular non-limiting embodiments,the dexmedetomidine is administered as a continuous infusion for lessthan about 72 hours, or less than about 48 hours, or less than about 36hours, or less than about 24 hours, or less than about 18 hours, or lessthan about 12 hours, or less than about 6 hours, or less than about 3hours, or less than about 1 hour, or less than about 30 minutes.

In certain embodiments, the method reduces the amount of rescuemedication required. In one embodiment, the rescue medication is anon-dexmedetomidine sedative. In particular embodiments, the presentlydisclosed method reduces the amount of sedative rescue medicationrequired by between about 5% and about 100%, or between about 5% andabout 75%, or between about 5% and about 50%, or between about 5% andabout 25%, or between about 5% and about 15%.

In particular embodiments, the sedative rescue medication is abenzodiazepine. Non-limiting examples of benzodiazepines includeclonazepam, diazepam, estazolam, flunitrazepam, lorazepam, midazolam,nitrazepam, oxazepam, triazolam, temazepam, chlordiazepoxide, andalprazolam. In particular embodiments, the sedative is a barbiturate.Non-limiting examples of barbiturates include amobarbital,pentobarbital, secobarbital, and phenobarbital. Other examples ofsedatives include chloral hydrate, eszopiclone, zaleplon, zolpidem, andzopiclone.

In certain embodiments, the rescue medication is an analgesic. Incertain embodiments, the method reduces the amount of analgesic rescuemedication required. In particular embodiments, the presently disclosedmethod reduces the amount of analgesic rescue medication required bybetween about 5% and about 100%, or between about 5% and about 75%, orbetween about 5% and about 50%, or between about 5% and about 25%, orbetween about 5% and about 15%.

In one embodiment, the analgesic is an opioid. Non-limiting examples ofopioids include codeine, oxycodone, hydrocodone, fentanyl, morphine,buprenorphine, hydromorphone, methadone, tramadol, meperidine,oxymorphone, and pentazocine. In certain embodiments, the analgesic isan N-methyl-D-aspartate antagonist (NDMA). Non-limiting examples ofNDMAs include ketamine, nitrous oxide, and xenon. Other examples ofanalgesics include clonidine, desflurane, isoflurane, and sevoflurane.The rescue medication may be administered via perioral, parenteral,transnasal (for example, a powder), rectal (for example, as asuppository), or topical administration.

In one embodiment, the presently disclosed method reduces incidence ofneurological damage. In particular embodiments, the presently disclosedmethod reduces the incidence of neurological damage in one or moreregions of the brain. Non-limiting examples of brain regions in whichthe incidence of neurological damage is reduced include cerebral cortex,basal ganglia, olfactory bulb, hypothalamus, thalamus, epithalamus,midbrain, pons, cerebellum, and medulla.

Non-limiting causes of neurological damage include, but are not limitedto, the administration of a sedative or analgesic agent, seizure,asphyxia, epilepsy, concussion, cerebral hemorrhage, cord shock,drowning, tumor, immunotherapy, chemotherapy, iatrogenic free-radicaltoxicity, injury, ataxias, surgery, cardiopulmonary bypass, cerebralpalsy, cerebral ischemia, cerebral anoxia injury, autoimmuneneurodegeneration, myocardial ischemia, myocardial infarct, stroke,atherosclerosis, acute respiratory failure, coronary artery bypassgraft, ulcerative colitis, traumatic brain injury, spinal cord injury,spinal muscular atrophy, vertebral disease, decompression sickness,fetal alcohol syndrome, hepatitis-B, hepatitis-C, hepatitis-G, yellowfever, dengue fever, encephalitis, liver disease, primary cirrhosis,renal disease, pancreatitis, polycystic kidney disease, H.pylori-associated gastric and duodenal ulcer disease, HIV infection,toxoplasmosis, rubella, cytomegalovirus, tuberculosis, meningitis,juvenile diabetes, lichenplanus, uveitis, Behcet's disease, pure redcell aplasia, aplastic anemia, amyotrophic lateral sclerosis, multiplesclerosis, nephrotic syndrome, and combinations thereof.

In particular non-limiting embodiments, the resulting neurologicaldamage includes various types of neurocognitive, psychocognitive, and/orneuromotor or motor impairment, or combinations thereof. Suchimpairments can be delayed functions or abilities, disrupted functionsor abilities, loss of function or ability, inability for develop orlearn new abilities, and the like. Non-limiting examples ofneurocognitive and/or psychocognitive impairments include learning,memory, executive function, and visuospatial ability impairment.Non-limiting examples of neuromotor impairments include strength,balance, mobility impairment, and combinations thereof. In othernon-limiting embodiments, the neurological damage includes developmentaldelay, cerebral palsy, mental retardation, visual impairment, hearingimpairment, autism, paralysis, hemiplegia, a strain condition, a stresscondition, a nervous dysfunction such as convulsions, seizure, musclestiffness, nervous strain and anxiety, and combinations thereof. (See,e.g., Hintz et al. Pediatrics. 2005 June; 115(6):1645-51.).

The neurological damage impairments may be assessed by well-establishedcriteria including but not limited to an IQ test (See, e.g., (Wechsler,J. Wechsler Preschool and Primary Scale of Intelligence. San Antonio:The Psychological Corp., 1989), the short-story module of the RandtMemory Test (See Randt C, Brown E. Administration manual: Randt MemoryTest. New York: Life Sciences, 1983), the Digit Span subtest and DigitSymbol subtest of the Wechsler Adult Intelligence Scale-Revised (SeeWechsler D. The Wechsler Adult Intelligence Scale-Revised (WAIS-R). SanAntonio, Tex.: Psychological Corporation, 1981.), the Benton RevisedVisual Retention Test (See Benton A L, Hansher K. Multilingual aphasiaexamination. Iowa City: University of Iowa Press, 1978), and the TrailMaking Test (Part B) (See Reitan R M. Validity of the Trail Making Testas an indicator of organic brain damage. Percept Mot Skills 1958;8:271-6). Other non-limiting examples of well-established criteria fordetermining neurological damage include the Bayley Scales of InfantDevelopment (BSID-II) Mental Development Index assessment, the BSID-IIPsychomotor Development Index assessment, the Denver DevelopmentalScreening Test, magnetic resonance imaging, vision tests, and hearingtests. Other tests can include standardized interaction and/orobservation, such as standardized assessments of socialization, hand-eyecoordination, motor control, ability to understand and use sounds andwords, and ability to recognize sounds and words.

Non-limiting examples of a reduction in the incidence of neurologicaldamage include a reduction in the severity of, reduction in the numberof, prevention of, or delay of the development of one or more incidencesof neurological damage, or a combination thereof. In one non-limitingembodiment, a reduction in the incidence of neurological damage includesa better score or assessment as measured by one of the tests orassessments listed above than if an effective amount of dexmedetomidinehad not been administered to the pediatric patient.

In particular embodiments, the neurological damage is cellulardegeneration or neuronal apoptosis. As used herein, the term “cellulardegeneration” refers to cell death as a result of a stimulus, trauma, apharmaceutical composition, or a pathologic process. As used herein, theterm “neuroapoptosis” or “neuronal apoptosis” refers to neuronal celldeath associated with programmed cell death. In particular embodiments,the methods reduce the incidence of neuroapoptosis.

Non-limiting examples of cells which can be protected by the presentlydisclosed methods include neurons and glial cells. Non-limiting examplesof neurons which can be protected by the presently disclosed methodsinclude Renshaw cells, Purkinje cells, hippocampal basket cells,cerebellum basket cells, cortex basket cells, cortex interneurons,cerebellum interneurons, pyramidal cells, granule cells, anterior horncells, and motor neurons. Non-limiting examples of glial cells which canbe protected by the presently disclosed methods include neurolemmocytes,satellite cells, microglia, oligodendroglia, and astroglia.

In certain embodiments, the neurological damage includes cell shrinkage,chromatin-clumping with margination, formation of membrane-enclosedapoptotic bodies, and Ash neuronal necrosis.

In one embodiment, the administration of dexmedetomidine reduces theincidence of neurological damage in a cortex lamina layer. In certainembodiments, the reduction occurs in one or more of the cortex laminalayers I-IV. In one embodiment, the reduction in neurological damageoccurs in a cortex lamina layer I. In particular embodiments, thereduction in neurological damage occurs in cortex lamina layer II. Incertain embodiments, the reduction occurs in both cortex lamina layer Iand II.

7. EXAMPLES

The following examples are merely illustrative of the presentlydisclosed subject matter and they should not be considered as limitingthe scope of the invention in any way.

Example 1: Dexmedetomidine Study in Neonates

Initial 30 Patient Study

A 30-subject, open-label, multicenter, safety, efficacy andpharmacokinetic study of dexmedetomidine was conducted on neonates aged≥28 weeks to ≤44 weeks gestational age who required sedation in anintensive care setting for a minimum of 6 hours. The present studyinvestigated the efficacy, pharmacokinetics, and safety ofdexmedetomidine safety at three different dose levels in neonates, ages≥28 weeks to ≤44 weeks gestational age, administered as a loading dosefollowed by continuous infusion for a minimum of 6 hours and up to 24hours in the neonatal intensive care unit (NICU), cardiac intensive careunit (CICU), or PICU. Gestation age (in weeks) was calculated as thetime elapsed between the first day of the last menstrual period and theday of enrollment. If pregnancy was achieved using assisted reproductivetechnology, gestational age was calculated by adding two weeks to thegestational age as calculated above.

The patients selected for the study were initially intubated andmechanically ventilated preterm neonates ≥28 weeks to <36 weeksgestational age and term neonates born at ≥36 weeks to ≤44 weeksgestational age. The former were assigned to Group 1 and the latter wereassigned to Group II. The subjects weighed over 1,000 g at the time ofenrollment.

The cardiovascular system in newborns has characteristics that couldnegatively impact the use of dexmedetomidine in this population. Unlikeolder infants, children, and adults, the newborn myocardium is not ableto increase contractility to increase cardiac output in response tometabolic demands. Instead, neonates are highly dependent on their HR toincrease cardiac output. As a result, bradycardia, a known effect ofdexmedetomidine, could decrease cardiac output in neonates. For thisreason, the doses selected for study in this population wereintentionally lower than those typically used for sedation of olderpediatric patients. The lower doses were expected to mitigate an adverseeffect of bradycardia, while the immaturity of the blood brain barrierin this population could facilitate the sedating properties ofdexmedetomidine because of its high lipid solubility and potentiallyhigher cerebrospinal fluid concentrations; therefore, the lowest dose,0.05 μg/kg loading dose over 10 or 20 minutes followed by 0.05 μg/kg hrmaintenance dose, was expected to effect some sedation in mechanicallyventilated subjects in this age group. The highest dose, 0.2 μg/kgloading dose followed by 0.2 μg/kg/hr, was not expected to causebradycardia.

Each subject received a loading dose of dexmedetomidine over 10 or 20minutes followed by the appropriate continuous infusion maintenance doseof dexmedetomidine for a minimum of 6 but not more than 24 hours. Thedose levels administered to each subject are given in Table 1 below.Subjects were sequentially assigned to the dose levels.

TABLE 1 Dose Levels for Each Age Group Treatment Group Age Group AgeGroup I ≥28 weeks II ≥36 weeks to <36 weeks to ≤44 weeks Continuous Dosegestational gestational Loading Infusion Rate Level age (n) age (n) Doseμg/kg μg/kg/hr 1 6 8 0.05 0.05 2 0 8 0.1 0.1 3 0 8 0.2 0.2

The dexmedetomidine administered was a Precedex® dexmedetomidine HClinjection manufactured by Hospira, Inc. Dexmedetomidine hydrochloride(HCl) injection (100 μg/mL, base) was supplied by Hospira to theinvestigative sites for infusion. Study medication was prepared(diluted) by the site pharmacy. The loading doses of dexmedetomidinewere diluted in 0.9% sodium chloride or dextrose 5% in water to one ofthe following concentrations: 4 μg/mL solution, 2 μg/mL solution, 1μg/mL solution, or 0.5 μg/mL solution. Dexmedetomidine was infused usinga controlled infusion device. In order to ensure proper infusion,dexmedetomidine was not administered directly into the pulmonary artery.

Dexmedetomidine was administered as a two-stage infusion. A 10- or20-minute loading dose infusion of dexmedetomidine was administeredfollowed by a continuous fixed maintenance dose infusion ofdexmedetomidine for a minimum of 6 and up to 24 hours post-operatively.The dexmedetomidine for maintenance infusion was diluted at the sameconcentration as for the loading dose of dexmedetomidine. Thedexmedetomidine for both the loading and the maintenance infusion wasadministered at the site of insertion of the IV catheter to avoidflushing the drug. Dexmedetomidine was administered through a designatedIV line for dexmedetomidine.

Sedation dosages were calculated using the subject's most recentlymeasured weight prior to commencement of dexmedetomidine. No dosageadjustments were needed for day to day weight fluctuations because thedexmedetomidine duration spanned a maximum of 24 hours.

Exposure to dexmedetomidine is summarized by gestational age in Table 2(loading dose), Table 3 (maintenance dose), and Table 4 (totaldose/time; time of exposure <6 hours, <12 hours, <24 hours, >0-<6 hours,≥6-<12 hours, ≥12-<24 hours, and ≥24 hours). Median exposure todexmedetomidine is summarized in Tables 2-4 below. The median data werechosen due to variability in data. Median dexmedetomidine exposure washighest in age Group II, dose level 3. For age Group I, 2 subjects eachreceived infusions lasting between >0-<6 hours, ≥6-<12 hours, and≥12-<24 hours. For age Group II, the majority of subjects (n=17, 70.8%)received infusions between ≥6-<12 hours, with a median duration of justover 6 hours (370 minutes). Subjects in dose level 3 received thelongest maintenance infusion in age Group II at a median of 961.5minutes (16 hours) compared to the other 2 cohorts in this age group ata median of 360.0-365.0 minutes (approximately 6 hours). All subjectscompleted the treatment, receiving a minimum of 6 hours of maintenanceinfusion.

TABLE 2 Median Loading Dose of Dexmedetomidine Exposure Age Group I^(a)Age Group II^(a) Dose Level 1 Dose Level 1 Dose Level 2 Dose Level 3dexmedetomidine dexmedetomidine dexmedetomidine dexmedetomidine TotalAge 0.05^(b) 0.05^(b) 0.1^(b) 0.2^(b) Group II^(a) Median Parameter (N =6) (N = 8) (N = 8) (N = 8) (N = 24) Loading dose N 6 8 8 8 24 Totalloading dose (μg) 0.07 0.18 0.31 0.70 0.31 Duration (min) 10.0 10.0 10.010.0 10.0 ^(a)Age Group I = ≥28 to <36 weeks gestational age; Age GroupII = ≥36 to ≤44 weeks. ^(b)Units are μg/kg for loading dose and μg/kg/hrfor maintenance dosing (continuous infusion).

TABLE 3 Median Maintenance Dose of Dexmedetomidine Exposure Age GroupI^(a) Age Group II^(a) Dose Level 1 Dose Level 1 Dose Level 2 Dose Level3 dexmedetomidine dexmedetomidine dexmedetomidine dexmedetomidine TotalAge 0.05^(b) 0.05^(b) 0.1^(b) 0.2^(b) Group II^(a) Median Parameter (N =6) (N = 8) (N = 8) (N = 8) (N = 24) Maintenance dose N 6 8 8 8 24 Totalmaintenance dose 1.30 1.08 1.87 12.20 1.87 (μg) Duration (min) 1407.5360.0 365.0 961.5 360.0 ^(a)Age Group I = ≥28 to <36 weeks gestationalage; Age Group II = ≥36 to ≤44 weeks. ^(b)Units are μg/kg for loadingdose and μg/kg/hr for maintenance dosing (continuous infusion).

TABLE 4 Median Total Dose of Dexmedetomidine Exposure Age Group I^(a)Age Group II^(a) Dose Level 1 Dose Level 1 Dose Level 2 Dose Level 3dexmedetomidine dexmedetomidine dexmedetomidine dexmedetomidine TotalAge 0.05^(b) 0.05^(b) 0.1^(b) 0.2^(b) Group II^(a) Median Parameter (N =6) (N = 8) (N = 8) (N = 8) (N = 24) Duration of exposure >0-<6 hours N 00 0 0 0 Total dose (μg) — — — — — Duration (min) — — — — — Duration ofexposure ≥6-<12 hours N 2 8 7 2 17 Total dose (μg) 0.51 1.26 2.14 4.061.52 Duration (min) 370.0 370.0 370.0 370.0 370.0 Duration of exposure≥12-<24 hours N 2 0 1 5 6 Total dose (μg) 1.97 — 7.76 13.32 12.96Duration (min) 1417.5 — 1370.0 1040.0 1070.0 Duration of exposure ≥24hours N 2 0 0 1 1 Total dose (μg) 1.35 — — 15.75 15.75 Duration (min)1450.0 — — 1460.0 1460.0 ^(a)Age Group I = ≥28 to <36 weeks gestationalage; Age Group II = ≥36 to ≤44 weeks. ^(b)Units are μg/kg for loadingdose and μg/kg/hr for maintenance dosing (continuous infusion).

Subjects in age Group I received a median total loading dose of 0.07 μgwith a median duration of 10 minutes and a median total maintenance doseof 1.30 μg over 1407.5 minutes (23.5 hours). Subjects in age Group IIreceived a median total loading dose of 0.18-0.70 μg over 10 minutes anda median total maintenance dose of 1.08-12.20 μg over 360-961.5 minutes(6-16 hours).

Efficacy evaluations were conducted by assessing the frequency ofsedation using the Neonatal Pain, Agitation, and Sedation Scale(N-PASS), developed to assess sedation and pain/agitation in neonates.The N-PASS includes 5 criteria to assess sedation levels, pain, andagitation in neonates. The indicators are as follows: 1)crying/irritability, 2) behavior/state, 3) facial expression, 4)extremities/tone, and 5) vital signs (i.e., HR, RR, SBP, DBP, and SpO₂).Whenever possible, the same Investigator or designee obtained N-PASSscores, according to the schedule of activities as shown in Table 5.

The evaluation for the presence of paradoxical reactions (notably rage)was monitored in conjunction with all N-PASS assessments. Rage wasprotocol-defined and occurred when either the Crying/Irritability orBehavior/State assessment criteria in the N-PASS merited a score of 2.For each of the 5 assessment criteria, the subject would be given onenumber, −2, −1, 0, +1, or +2. The subject might have some criteria scorein the negative sedation side, and other criteria in the positivepain/agitation side, but for a single criterion would score either onthe sedation or the pain side, not both. If subject gestational age was<30 weeks, 1 was added into the pain score.

TABLE 5 N-PASS—Neonatal Pain, Agitation and Sedation Scale AssessmentSedation Sedation/Pain Pain/Agitation Criteria −2 −1 0/0 1 2 Crying Nocry with Moans or cries No sedation/ Irritable or High-pitched orIrritability painful stimuli minimally No pain signs crying atsilent-continuous with painful intervals cry Inconsolable stimuliConsolable Behavior No arousal to Arouses No sedation/ Restless,Arching, kicking State any stimuli minimally to No pain signs squirmingConstantly awake or No stimuli Awakens Arouses spontaneous Littlefrequently minimally/no movement spontaneous movement (not movementsedated) Facial Mouth is lax Minimal No sedation/ Any pain Any painExpression No expression expression No pain signs expression expressionwith stimuli intermittent continual Extremities No grasp reflex Weakgrasp No sedation/ Intermittent Continual Tone Flaccid tone reflex Nopain signs clenched clenched toes, ↓ muscle tone toes, fists or fists,or finger finger splay splay Body is not Body is tense tense Vital SignsNo variability <10% No sedation/ ↑ 10-20% ↑ >20% from HR, RR, withstimuli variability No pain signs from baseline BP, Hypoventilation frombaseline baseline SaO₂ ≤75% with SaO₂ or apnea with stimuli SaO₂ 76-stimulation - slow 85% with ↑ stimulation - Out of quick ↑ sync/fightingvent

Morphine or fentanyl and/or midazolam could be given for rescue asindicated by a total N-PASS score >3 or by clinical judgment. Thedexmedetomidine infusion could be continued during and after the subjectwas extubated; however, the minimum duration of dexmedetomidine infusionwas 6 hours and the maximum duration of infusion was 24 hours. Efficacymeasures included the use of rescue medication for sedation or analgesia(incidence and amount used) during dexmedetomidine infusion.

Rescue medication was administered as needed for sedation (midazolam)and pain (fentanyl or morphine), during dexmedetomidine administrationbased on results of the N-PASS sedation/pain scale. Rescue therapy wasindicated when the N PASS total score >3 and the selection of sedativerescue or analgesic rescue was at the discretion of the Investigator.For any bolus administration of rescue therapy, the following sequenceof events occurred: The N-PASS score was obtained prior to theadministration of rescue medication and within 5 minutes afteradministration of midazolam. The rescue medicine for sedation wasmidazolam and the rescue medication for pain was either fentanyl ormorphine. Midazolam was administered based on labeling for pediatrics ata recommended dose of 0.05 to 0.15 mg/kg per dose. Rescue fentanyl forpain was administered in a 0.5 to 2 μg/kg bolus or 1 to 2 μg/kg/hrcontinuous infusion. For continuous infusions of fentanyl, the N-PASSwas recorded immediately prior to initiating the continuous infusion.Rescue morphine was administered as a 0.025 to 0.1 mg/kg bolus or 0.01to 0.02 mg/kg/hr continuous infusion. For continuous infusions ofmorphine, the N-PASS was recorded immediately prior to initiating thecontinuous infusion.

Summary statistics for the dexmedetomidine loading doses and maintenanceinfusion doses are shown in Table 8A below.

TABLE 5A Summary Statistics of Dosing-Related Data 0.05 μg/kg + 0.10μg/kg + 0.20 μg/kg + Dose-Related Variable 0.05 μg/kg/h 0.10 μg/kg/h0.20 μg/kg/h Loading dose (ng) Mean (SD) 125.400 (58.239) 298.650(51.136)   664.250 (114.030) Median 120.000 312.000 676.000 Min, Max56.00, 217.50 200.10, 363.00 460.00, 830.00 n 10 8 8 Maintenanceinfusion Mean (SD) 1147.563 (546.668) 2513.618 (2004.047) 10579.833(5174.104) dose (ng) Median 1080.000 1872.000 12195.750 Min, Max 357.00,2197.67 1317.33, 7425.00  2760.00, 16756.00 n 10 8 8 Total dose (ng)Mean (SD) 1272.963 (548.969) 2812.268 (2023.889) 11244.083 (5249.609)Median 1260.000 2184.000 12960.750 Min, Max 416.50, 2292.67 1517.43,7755.00  3220.00, 17464.00 n 10 8 8 Loading infusion Mean (SD)  0.167(0.000) 0.229 (0.086)  0.208 (0.077) duration (h) Median 0.167 0.1670.167 Min, Max 0.17, 0.17  0.17, 0.33 0.17, 0.33 n 10 8 8 Maintenanceinfusion Mean (SD) 11.292 (8.523) 8.223 (5.774) 15.454 (6.887) duration(h) Median 6.000 6.083 16.025 Min, Max 6.00, 24.00  6.00, 22.50  6.00,24.00 n 10 8 8 Time between start of Mean (SD)  18.500 (20.823) 14.500(4.629)  13.125 (4.291) doses (min) Median 10.000 12.000 11.000 Min, Max10.00, 75.00  10.00, 20.00 10.00, 20.00 n 10 8 8 Time from end of 1^(st)Mean (SD)  8.500 (20.823) 0.750 (1.035)  0.625 (0.744) to beginning of2^(nd) Median 0.000 0.500 0.500 infusion (min) Min, Max 0.00, 65.000.00, 3.00 0.00, 2.00 n 10 8 8

Safety measures included collection of adverse events (adverse events),heart rate (HR in beats per minute [bpm]), systolic blood pressure (SBPin millimeters of mercury [mmHg]), diastolic blood pressure (DBP inmillimeters of mercury [mmHg]), mean arterial pressure (MAP inmillimeters of mercury [mmHg]), oxygen saturation by pulse oximetry(SpO₂ in percentage), and respiratory rate (RR in breaths/minute[breaths/min]) or ventilator settings, laboratory results, andelectrocardiogram (ECG) monitoring.

Arterial, venous, or capillary blood samples (0.15 mL each) forpharmacokinetic analysis were obtained at six or sevenprotocol-designated times for subjects in age Group I depending uponweight (≥28 weeks to <36 weeks gestational age) and at seven designatedtimes for subjects in age Group II (≥36 weeks through ≤44 weeksgestational age).

Chemistry, hematology and urinalysis samples were obtained for thelaboratory tests according to the following schedule of studyactivities: at screening, after five hours of maintenance but beforediscontinuation of dexmedetomidine and within 24 hours following thediscontinuation of dexmedetomidine infusion. In addition, subjects whowere s/p CPB had a sample drawn for ALT level following CPB, but nolater than 1 hour from the commencement of dexmedetomidine (thisconstituted the ALT at baseline). All blood and urine samples werecollected in appropriately labeled tubes and sent to the locallaboratory for analysis.

Liver function tests (LFTs) were obtained pre- and post treatment andcompared for evidence of hepatic dysfunction. Liver function tests wereobtained during the following periods: at screening, after five hours ofmaintenance but before discontinuation, and in close proximity to 24hours after discontinuation of the infusion or on the day of discharge,whichever came first. In addition, subjects who were s/p CPB had asample drawn for ALT level following CPB, but no later than 1 hour fromthe beginning of the dexmedetomidine infusion. This constituted the ALTat baseline and was not used in reference to exclusion criteria. Liverfunction tests were defined as: aspartate aminotransferase (AST), ALT,alkaline phosphatase, and total bilirubin. Hepatotoxicity was defined byan ALT >156 U/L or a ≥30% increase from screening value, whichever wasgreater.

The statistical analyses were performed using SAS' Statistical SoftwareSystem (SAS Institute, Inc., Cary, N.C.), version 9.1. All statisticaltests were 2 sided and p values ≤0.0500, after rounding to 4 decimalplaces, were considered statistically significant unless otherwisespecified. In general, missing data were not imputed. For continuousvariables, N, mean, median, SD, minimum, Q1, Q3 and maximum arepresented. The mean and median was displayed to 1 decimal place morethan the raw value. The standard deviation (SD) is displayed to 2decimal places more than the raw value. For categorical variables, N andpercent is shown. All percentages were reported to 1 decimal place.

For the final analyses, treatment differences by age groups wereassessed for continuous variables using two-way analysis of variance(ANOVA) when assumption of normal distribution is reasonable or bynonparametric tests when this assumption was not met. For orderedcategorical variables, the Cochran-Mantel-Haenszel (CMH) test was used.If treatment differences are significant, a pairwise comparison betweendose levels was performed. All efficacy variables were analyzed while ondexmedetomidine.

Dexmedetomidine was effective at sedating critically ill, initiallyintubated and mechanically ventilated premature infants, ≥28 to <36weeks. No subject in age Group I received rescue midazolam for sedationduring dexmedetomidine infusion. At the doses used in this trial, up to0.2 μg/kg/hr, dexmedetomidine was moderately effective at sedating termneonates. In age Group II, a total of 4 subjects (16.7%) received rescuemidazolam (mean dose 0.22 mg/kg) for sedation during dexmedetomidineinfusion.

Most premature neonates in age group I did not require additionalmedication for pain while on dexmedetomidine infusion. One subject(16.7%) in age group I received rescue medication for analgesia duringthe study infusion. In contrast, more of the term neonates in age groupII (58.3%) received rescue medication for analgesia during the studyinfusion. The increased analgesic requirements in age group II, inparticular dose level 3, most likely reflects the higher proportion ofpost-operative surgical subjects.

All dose levels spent a low period of time with a total N-PASS score >3indicating most subjects were adequately sedated and not manifestingsigns of pain/agitation. Generally, trends in mean change from baselinein vital signs were not clinically meaningful.

Premature neonates, ≤28 to <36 weeks gestational age, appeared to havelower clearance than term neonates which resulted in higherdose-adjusted exposure. These parameters were well estimated at 1 doselevel (0.05 μg/kg) for age Group I (≥28 to <36 weeks gestational age)and for all 3 dose levels (0.05 μg/kg, 0.1 μg/kg, and 0.2 μg/kg) for ageGroup II (≥36 to ≤44 weeks gestational age). The younger subjectsappeared to have lower clearance (0.41 L/hr/kg at 0.05 μg/kg dose levelin age Group I) than older subjects (0.61 L/hr/kg at 0.05 μg/kg doselevel in age Group II) which resulted in higher dose-adjusted exposure.This finding is difficult to interpret because of the lack ofpharmacokinetic data available at the 0.1 μg/kg and 0.2 μg/kg doselevels in the younger subjects.

The results of the pharmacokinetic analysis suggest volume ofdistribution at steady state, weight adjusted (V_(ssw)) and the apparentterminal elimination half-life (t_(1/2)) were similar across dose levelsand age groups. In addition, dexmedetomidine exposure appeared to bedose proportional within the older subjects (age Group II). Doseproportionality within the younger subjects (age Group I) could not beassessed. This finding is difficult to interpret because of the lack ofpharmacokinetic data available at the 0.1 μg/kg and 0.2 μg/kg doselevels in the younger subjects. The lower clearance in this age groupand higher concentrations are consistent with the greater efficacyobserved in the premature neonates (no subjects required rescuemidazolam for sedation and 1 subject required rescue medication foranalgesia) compared to the term neonates (4 subjects required rescuemidazolam for sedation and 14 subjects required rescue medication foranalgesia). The V_(ssw) and the t_(1/2) were similar across dose levelsand age groups.

Dexmedetomidine was safe and well tolerated in both age groups and atall doses. The adverse effect profile observed is typical of thecritically ill, high risk pediatric population and post-operativesurgical patients. Treatment-emergent adverse effects were experiencedby 2 subjects (33.3%) in age Group I and by 15 subjects (62.5%) in ageGroup II. In age Group I, dose level 1, no treatment-emergent adverseeffects were reported by more than 1 subject. In age Group II, eventsreported by more than 1 subject were hypokalemia, decreased bloodpotassium, anger, atelectasis, and pleural effusion. These events weremore common and expected in the post-operative open heart surgerysubjects.

The time to successful extubation was explored in Precedex-exposedsubjects using Kaplan-Meier estimates. Results for this section are notclinically meaningful and therefore are not further discussed due to thehigh variability in medical history factors.

Most treatment-emergent adverse effects were assessed as not related totreatment, only 2 subjects in the study (in age Group II) experiencedtreatment-emergent adverse effects assessed as related to treatment.There were no severe treatment-emergent adverse effects reported, 2subjects in each age group experienced moderate treatment-emergentadverse effects, all other subjects experienced mild treatment-emergentadverse effects. There were no treatment-emergent serious adverseeffects leading to death, no other treatment-emergent serious adverseeffects, and no treatment-emergent adverse effects that led todexmedetomidine discontinuation. There were no dose-limiting toxicitiesthat led to dexmedetomidine discontinuation (persistent bradycardia,persistent hypotension, or respiratory depression).

In general, mean changes from baseline were not clinically significantfor laboratory parameters, vital signs, physical examination, or ECGs.Dexmedetomidine was effective at sedating critically ill, initiallyintubated and mechanically ventilated premature infants. No subject inage Group I received rescue midazolam for sedation during the studyinfusion. At the doses used in this trial, up to 0.2 μg/kg/hr,dexmedetomidine was moderately effective at sedating term neonates. Mostpremature neonates in age Group I did not require additional medicationfor pain while on dexmedetomidine infusion. In contrast, more of theterm neonates in age Group II (58.3%) received rescue medication foranalgesia during the study infusion. The increased analgesicrequirements in age Group II, in particular dose level 3, most likelyreflects the higher proportion of post-operative surgical subjects.Premature neonates appeared to have lower plasma clearance than termneonates which resulted in higher dose-adjusted exposure and greaterefficacy. No subjects discontinued the trial due to treatment-emergentadverse effects. Dexmedetomidine was safe and well tolerated in both agegroups and at all doses. The adverse effect profile observed is typicalof the critically ill, high risk pediatric population studied.

Additional 6 Patient Cohort

After the study had been initiated with the first original 30 patients,an additional six patients were enrolled in and completed the study(hereinafter the “additional cohort”). The study protocol for the studyconducted on the additional cohort is as described above. The additionalsix patients were neonates aged ≥28 weeks to <36 weeks gestational agethat required sedation in an intensive care setting for a minimum of 6hours. These six patients were in dose level 2 and received a loadingdose of 0.1 μg/kg and a maintenance dose of 0.1 μg/kg. The dose levelsfor each age group for the 36 total patients that receiveddexmedetomidine in this study are given in Table 6 below.

TABLE 6 Dose Levels for Each Age Group Treatment Group Age Group AgeGroup I ≥28 weeks II ≥36 weeks to <36 weeks to ≤44 weeks Continuous Dosegestational gestational Loading Infusion Rate Level age (n) age (n) Doseμg/kg μg/kg/hr 1 6 8 0.05 0.05 2 6 8 0.1 0.1 3 0 8 0.2 0.2

The mean gestational age for the 6 subjects in the additional cohort was32.5 weeks. There were 3 males and 3 females. The mean weight was 1.71kg and the mean height was 42.75 cm. The reason for intubation wasrespiratory disease in 5 of the subjects and sepsis in 1 subject.

All 6 subjects in the additional cohort had received prior therapiesbefore entering this study; the most common of these wereanti-infectives, nutrition products, and midazolam or fentanyl. All 6subjects received concomitant therapies; the most common of these wereanti-infectives and nutrition products. All 6 subjects received a widevariety of therapies post-dexmedetomidine infusion.

None of the 6 subjects in the additional cohort required rescuemidazolam or morphine during the dexmedetomidine infusion. Only onesubject (16.7%) required rescue medication for analgesia during thedexmedetomidine infusion and was administered 2 μg (0.98 μg/kg)fentanyl. The duration of the dexmedetomidine infusion in this subjectwas 6.5 hours. This subject had a medical history of gastroschisisrequiring surgery for placement of a silo as well as respiratorydistress syndrome requiring intubation, both ongoing at the time ofscreening. The subject requiring rescue analgesia was the only subjectto have a total N-PASS score below 3, which the subject had for 0.25hours due to an infiltrated I.V.

The geometric means of plasma pharmacokinetic parameters ofdexmedetomidine following a loading dose and a maintenance dose in thecohort for the study addendum (age group I, dose level 2) are shown inTable 7 below.

TABLE 7 Geometric Mean Plasma Pharmacokinetic Parameters for AdditionalCohort Patients Age Group I^(a) Dose Level 2 DEX Loading Dose = 0.1μg/kg Pharmacokinetic Parameter Maintenance Dosing = 0.1 (units)μg/kg/hr (N = 6) CL (L/hr) 0.48 (n = 2) CL_(w) (L/hr/kg) 0.29 (n = 2)AUC (0-Last) [(pg/mL)hr] 708.09 AUC (0-Infinity) [(pg/mL)hr] 4305.31 (n= 2)   AUC (0-Infinity)_(Dose) 2102.55 (n = 2)   [(pg/mL)hr/μg] C_(max)(pg/mL) 107.22 V_(d) (L) 5.71 (n = 2) V_(dw) (L/kg) 3.47 (n = 2) V_(ss)(L) 6.25 (n = 2) V_(ssw) (L/kg) 3.79 (n = 2) t_(1/2) (hr) 8.32 (n = 2)^(a)Age group I = ≥28 to <36 weeks gestational age

The weight adjusted clearance (CL_(w)) of DEX in the 2 subjectsevaluated in the additional cohort was similar to the 1 subjectevaluated in age group I, dose level 1 and again lower than observed inage group II subjects. Consistent with the difference in clearance, thedose-adjusted area under the concentration-time curve from zero toinfinity, AUC (0-Infinity), evaluated in the additional cohort (n=2),was 4.6 times higher (2102.55 versus 461.04 (pg/mL)hr than thatcalculated for age group II across all dose levels (n=12). In a similarmanner, the concentration at steady-state (C_(ss)) was higher in theadditional cohort than in the same dose level in age group II (369.67versus 170.53 μg/mL). However, the maximum concentration (C_(max)) wasactually lower in the additional cohort versus the same dose level inage group II, 107.22 versus 122.43 μg/mL, respectively. The weightadjusted volume of distribution at steady-state (V_(ssw)) was slightlylarger in the additional cohort compared to the same dose level in agegroup II (3.79 versus 2.85 L/kg) and the apparent terminal eliminationhalf-life (t_(1/2)) was longer at 8.32 versus 4.77 hours, respectively.

Dexmedetomidine was safe and well tolerated in both age groups and atall doses, including the additional cohort. The adverse events profileobserved in the additional cohort is typical of the critically ill, highrisk pediatric population.

The limited information from the premature neonates makes interpretationof the effect of age on the pharmacokinetics of dexmedetomidinedifficult. However, based on the two dose levels (0.05 and 0.1 μg/kg)tested in age group 1 in the original 30 patient group and theadditional cohort, it appeared that clearance was lower, which resultedin total exposure (AUC) that was 4.4 to 4.6 times larger in thepremature neonates (n=3) than the term neonates (n=12). This finding isalso consistent with higher C_(ss) levels in the premature neonates inage group I, dose levels 1 and 2 compared to the term neonates. Thelower clearance in the premature neonates and higher concentrations areconsistent with the greater efficacy observed in the premature neonatesin both dose levels (no subjects required rescue midazolam for sedationand 2 subjects required rescue medication for analgesia) compared withthe term neonates (4 subjects required rescue midazolam for sedation and14 subjects required rescue medication for analgesia).

The C_(max) and AUC (0-last) appeared lower in the additional cohortcompared to the same dose level from the age group II population. Thesevalues were: C_(max) 107.22 versus 122.43 μg/mL and AUC(0-Last) 708.09versus 813.26 (pg/mL)hr, respectively. Lower clearance, higherconcentrations, and greater efficacy were observed in the additionalcohort of premature neonates and consistent with what was observed inthe other premature neonate cohort compared to the term neonates in theoriginal 30 patient population.

Most premature neonates in age group I in the additional cohort and inthe original 30 patient population data did not require additionalmedication for pain while on dexmedetomidine infusion. One subject(16.7%) in each dose level of age group 1 received rescue medication foranalgesia during the study infusion. In contrast, in the original 30patient population, more of the term neonates in age group II (58.3%)received rescue medication for analgesia during the study infusion. Theincreased analgesic requirements in age group II, in particular doselevel 3, most likely reflects the higher proportion of postoperativesurgical subjects. Subjects in the additional cohort and in the original30 patient population data spent a low period of time with a totalN-PASS score >3, indicating that most subjects were adequately sedatedand not manifesting signs of pain/agitation. Generally, trends inchanges from baseline in vital signs in the additional cohort and in theinterim analyses data were not clinically meaningful.

Median exposure to dexmedetomidine is summarized in Table 8 below. Themedian data were chosen due to variability in data. Subjects in agegroup I, dose level 2 had a lower median total maintenance dose andduration of dexmedetomidine exposure compared to age group I, dose level1 from the interim analyses: specifically, 1.14 μg versus 1.30 μg with amedian duration of 375.0 minutes (6.25 hours) versus 1407.5 minutes(23.5 hours), respectively.

Subjects in age group I, dose level 2 had a lower median totalmaintenance dose but similar duration of dexmedetomidine exposurecompared with age group II from the interim analyses at the same doselevel: specifically, 1.14 μg versus 1.87 μg with a median duration of375.0 minutes (6.25 hours) versus 365.0 minutes (6.1 hours),respectively. Five of the 6 subjects received infusions lasting ≥6-<12hours with a median dose of 1.26 μg and duration of 380 minutes (6.3hours) and 1 subject ≥12-<24 hours received a total dose of 4.06 μg andduration of 1285.0 minutes (21.4 hours). All subjects completed thetreatment, receiving a minimum of 6 hours of maintenance infusion.

TABLE 8 Median Dose and Duration of Dexmedetomidine Exposure Age Group1^(a) Median Parameter Dose Level 2 DEX 0.1^(b) (N = 6) Loading dose N 6Total loading dose (μg) 0.18 Duration (min) 20 Maintenance dose N 6Total maintenance dose (μg) 1.14 Duration (min) 375.0 Duration ofexposure ≥6-<12 hours N 5 Total dose (μg) 1.26 Duration (min) 380.0Duration of exposure ≥12-<24 hours N 1 Total dose (μg) 4.06 Duration(min) 1285.0 ^(a)Age group I = ≥28 to <36 weeks gestational ages.^(b)Units are μg/kg for loading dose and μg/kg/hr for maintenance dosing(continuous infusion).

There was variability between subjects for most hematology tests. Ingeneral, no evidence of systematic change for any hematologic variable,chemistry variable, or urinalysis variable were found.Treatment-emergent adverse events pertaining to laboratory results werehypoalbuminemia (n=3) and the following events that occurred in onesubject each: hyperbilirubinemia, increased unconjugated bloodbilirubin, hypoproteinemia, hypocalcemia, hematuria, and hyperglycemia.All of these laboratory parameters were assessed as not related todexmedetomidine and are typical of this premature neonate population.Physical examination data was collected. The most common abnormalfindings at screening and post-dexmedetomidine administration were inthe pulmonary/respiratory system. There were no abnormal, clinicallysignificant electrocardiogram results at screening, during, orpost-dexmedetomidine administration. Total fluid input ranged from 49.1to 162.6 mL and total fluid output ranged from 30 to 224 mL. In general,changes from baseline were not clinically meaningful for laboratoryparameters, vital signs, physical examination, or electrocardiogramresults in the additional cohort.

Treatment-emergent adverse events were experienced by all 6 subjects inthe additional cohort, which are given in Table 9 below. Of the 18treatment-emergent adverse events reported, only hypoalbuminemia (n=3)was reported in more than one subject. Most treatment-emergent adverseevents were assessed as not related to treatment. The onlytreatment-emergent adverse events that were assessed as related todexmedetomidine were mild. One subject experienced twotreatment-emergent adverse events assessed as related to treatment. Onesubject experienced three severe treatment-emergent adverse events; twosubjects experienced 1 moderate treatment-emergent adverse event each.None of these severe or moderate events were assessed as related todexmedetomidine. All other events were mild. There were notreatment-emergent serious adverse events leading to death, one subjectexperienced three treatment emergent serious adverse effects, and nosubjects had treatment-emergent adverse events that led todexmedetomidine discontinuation. There were no treatment emergentdose-limiting toxicities that led to dexmedetomidine discontinuation(persistent bradycardia, persistent hypotension, or respiratorydepression).

TABLE 9 Summary of Treatment Emergent Adverse Events by System OrganClass and Preferred Term Dose Level 2 System Organ Class PreferredTerm^((a)) Dex 0.1 (N = 6) Number of Events 18 Number of Subjects withat least one event  6 (100.0%) Cardiac disorders 1 (16.7%) Bradycardia 11 (16.7%) Cardio-respiratory arrest 1 (16.7%) General disorders andadministration site conditions 2 (33.3%) Infusion site extravasation 1(16.7%) Oedema 1 (16.7%) Hepatobiliary disorders 1 1 (16.7%)Hyperbilirubinaemia 1 (16.7%) Infections and infestations 1 (16.7%)Sepsis 1 (16.7%) Investigations 2 (33.3%) Blood bilirubin unconjugatedincreased 1 (16.7%) Oxygen saturation decreased 1 (16.7%) Metabolism andnutrition disorders 3 (50.0%) Hyperglycaemia 1 (16.7%) Hypoalbuminaemia3 (50.0%) Hypocalcaemia 1 (16.7%) Hypoproteinaemia 1 (16.7%) Psychiatricdisorders 1 (16.7%) Anger 1 (16.7%) Renal and urinary disorders 1(16.7%) Haematuria 1 (16.7%) Note: Percentages are based on the numberof subjects in each dose level and age group. Subjects are counted oncewithin each system organ class or for each preferred term and may havehad more than one adverse event. ^((a))All investigator adverse eventterms were coded using MedDRA dictionary version 13.0.

The mean gestational age for group I-level 1 and 2 was 30.3 and 32.5 wksand for group II-levels 1-3, 38.7 wks. Adequate level of sedation wasseen in most patients and rescue sedation with midazolam (0.22±0.26mg/kg) was given only in 4 patients (17%) in group II. Rescue analgesiawith fentanyl was given in 2 (17%) patients in group I, and 11(46%)patients in group II. Additionally 4 (21%) patients in group II receivedrescue morphine. In group I, level 1 and 2, dexmedetomidine clearance(CL_(w)) was 0.41 and 0.29 L/hr/kg, maximum plasma concentration(C_(max)) was 102 and 107 μg/mL, volume of distribution (V_(ssw)) was2.7 and 3.8 L/kg, and elimination t_(1/2) 3 and 8 hrs respectively. Ingroup 2, level 1, 2 and 3 CL_(w) was 0.61, 0.64 and 0.73 L/hr/kg,C_(max) was 78, 122, 325 μg/mL, V_(ssw) 1.4, 2.8 and 2 L/kg, and t/3, 5and 3 hrs respectively. A lower CL_(w) was observed in group I alongwith a total exposure (AUC) that was 4.5 times larger than group II. Thesafety profile observed was typical of the critically ill, high riskpediatric population and post-operative surgical patients. Adverseevents were reported in 8 (67%) patients in group I and 15 (62%)patients in group II but in only 2 (8%) patients these adverse eventswere assessed as related to dexmedetomidine. None had serious adverseevents related to dexmedetomidine or adverse events needingdexmedetomidine discontinuation.

The overall efficacy conclusions of the study were not affected by theupdate with the additional cohort. Dexmedetomidine was effective atsedating critically ill, initially intubated and mechanically ventilatedpremature infants, ≥28 to <36 weeks, in the additional cohort and inoriginal 30 patient population. No subject in the original 30 patientpopulation or the additional cohort in age group I, dose levels 1 or 2,received rescue midazolam for sedation during dexmedetomidine infusion.In the original 30 patient population, at the doses used in this trial,up to 0.2 μg/kg/hr, dexmedetomidine was effective at sedating termneonates. In age group II, a total of 4 subjects (16.7%) received rescuemidazolam (mean dose 0.22 mg/kg) for sedation during dexmedetomidineinfusion.

Most premature neonates in age group I in the additional cohort and inthe interim analyses data did not require additional medication for painwhile on dexmedetomidine infusion. One subject (16.7%) in each doselevel of age group 1 received rescue medication for analgesia during thestudy infusion. In contrast, in the interim analyses, more of the termneonates in age group II (58.3%) received rescue medication foranalgesia during the study infusion. The increased analgesicrequirements in age group II, in particular dose level 3, most likelyreflects the higher proportion of postoperative surgical subjects.

Subjects in the additional cohort and in the interim analyses data spenta low period of time with a total N-PASS score >3 indicating mostsubjects were adequately sedated and not manifesting signs ofpain/agitation.

Lower clearance, higher concentrations, and greater efficacy wereobserved in the additional cohort of premature neonates and consistentwith what was observed in the other premature neonate cohort in theinterim analyses compared to the term neonates in the interim analyses.

Subjects in the additional cohort of age group I, dose level 2, had alower median total maintenance dose and duration of dexmedetomidineexposure compared to age group I, dose level 1 in the interim analyses.The additional cohort of subjects also had a lower median totalmaintenance dose but similar duration of dexmedetomidine exposurecompared to age group II at the same dose level.

Example 2: Dexmedetomidine Study in Pediatric Intensive Care UnitSubjects

A 175-subject, randomized, double-blind, dose-controlled, multicenterstudy of dexmedetomidine was conducted on initially intubated andmechanically ventilated pediatric subjects in the pediatric intensivecare setting. The present study investigated the efficacy,pharmacokinetics, and safety of dexmedetomidine at four different doselevels. The subjects were between the ages of 1 month and less than 17years. For neonates who were born prematurely, the age was correctedbased on gestational age until 3 months of actual birth age. Thesubjects were mechanically ventilated prior to and during thecommencement of dexmedetomidine, and were anticipated to require aminimum of 6 hours of continuous intravenous (IV) sedation. The subjectscould be intubated by nasotracheal, endotracheal or via tracheotomy.

Subjects also had to have an American Association of Anesthesiologists(ASA) classification of 1, 2, 3, or 4, and a University of MichiganSedation Scale (UMSS) score of 1, 2, 3, or 4 at the start of infusion ofdexmedetomidine.

Subjects were randomized into one of two treatment groups. Within eachtreatment group, the loading and maintenance doses were stratifiedaccording to the presence or absence of cardiopulmonary bypass (CPB).The treatment groups are given in Table 10 below. A total of 89 subjectswere randomized to Group 1 (low dose) and 86 were randomized to Group 2(high dose). Of these, 83 subjects in the low dose group and 81 subjectsin the high dose received randomized dexmedetomidine for at least 6hours.

TABLE 10 Doses of Dexmedetomidine Diagnosis Group 1 Low dose Group 2High dose s/p CPB Loading dose: Loading dose 0.2 μg/kg 0.5 μg/kgMaintenance dose titration Maintenance dose titration range (0.025-0.5μg/kg/hr) range (0.1-0.7 μg/kg/hr) All other Loading dose Loading dosediagnoses 0.3 μg/kg 0.6 μg/kg Maintenance dose titration Maintenancedose titration range (0.05-0.5 μg/kg/hr) range (0.2-1.4 μg/kg/hr)

The median age of age groups combined was 10.7 months (range: 0.9 monthsto 16.3 years) in the low dose group and 14.7 months (range: 1.3 monthsto 16.2 years) in the high dose group. Height and weight were similaracross dose groups and by underlying condition (median height of agegroups combined: low dose 68.0 cm, high dose 76.5 cm; median weight ofage groups combined: low dose 8.1 kg; high dose 8.5 kg). Slightly moresubjects overall were male than female (low dose, 59.6% male; high dose,55.8% male). Demographics were similar between treatment groups withmost subjects critically ill from severe congenital cardiopulmonarydisease (ASA P3).

Patients were further assigned to age group I or II. The number ofsubjects in each subgroup is given in Table 11 below.

TABLE 11 Number of Subjects in Each Subgroup (Enrolled Subjects) Group 1Low Dose Group 2 High Dose s/p Other s/p Other CPB^(a) Dx^(b) TotalCPB^(c) Dx^(d) Total N = 36 N = 53 N = 89 N = 37 N = 49 N = 86 Age GroupI^(e) 25 38 63 26 34 60 Age Group II^(f) 11 15 26 11 15 26 Total 36 5389 37 49 86 Dx = diagnosis ^(a)Dex dose is loading dose (LD) =0.2/Maintenance dose (MD) = 0.025-0.5 μg/kg/hour ^(b)Dex dose is LD =0.3/MD = 0.05-0.5 μg/kg/hour ^(c)Dex dose is LD = 0.5/MD = 0.1-0.7μg/kg/hour ^(d)Dex dose is LD = 0.6/MD = 0.2-1.4 μg/kg/hour ^(e)Agegroup I = ≥1 month to <24 months; ^(f)Age group II = ≥24 months to <17years old

In age group I, median age was 8.51 months (low dose) and 9.75 months(high dose); in age group II, median age was 6.32 years (low dose) and7.57 years (high dose). Subjects had similar screening ASAclassification in both age groups and both dexmedetomidine dose groupswith the majority of subjects having high risk with severe systemicdisease, P3. Subjects who underwent open-heart surgery were mostly highrisk P3 and there were similar numbers of subjects in the low dose(72.2%) and high dose (73.0%) dexmedetomidine.

All subjects (100.0%) in the high dose group and all except one subjectin the low dose group received at least one concomitant medicationduring the study; concomitant medication use was similar across dosegroups. Concomitant medications taken by at least 50.0% of subjects in adose group, excluding midazolam, fentanyl, and morphine, the use ofwhich was permitted as rescue medication per protocol, were furosemide,acetaminophen, potassium chloride, and heparin. As expected in the s/pCPB groups following open heart surgery, >90% of subjects were oninotropic support postoperatively. Inotropic support with milrinone anddobutamine was similar in both the low and high dose dexmedetomidinegroups s/p CPB.

Subjects received an optional loading dose of dexmedetomidine over 10 or20 minutes followed by the appropriate maintenance dose. Each subjectreceived a continuous infusion maintenance dose of dexmedetomidine for aminimum of 6 but not more than 24 hours.

The dexmedetomidine administered was a Precedex® dexmedetomidine HClinjection manufactured by Hospira, Inc. For subjects s/p CPB, the lowdose dexmedetomidine group was titrated between 0.025-0.5 μg/kg/hr andthe high dose dexmedetomidine group was titrated between 0.1-0.7μg/kg/hr; for all other diagnoses, the low dose dexmedetomidine groupwas titrated between 0.05-0.5 μg/kg/hr and the high dose dexmedetomidinegroups was titrated between 0.2-1.4 μg/kg/hr. The continuous infusion ofdexmedetomidine was administered for a minimum of 6 and a maximumduration of 24 hours.

The dexmedetomidine administered was a Precedex® dexmedetomidine HClinjection manufactured by Hospira, Inc. Dexmedetomidine hydrochloride(HCl) injection (100 μg/mL, base) was supplied by Hospira to theinvestigative sites for infusion. Study medication was prepared(diluted) by the site pharmacy. The optional loading doses ofdexmedetomidine were diluted in 0.9% sodium chloride or dextrose 5% inwater to one of the following concentrations: 4 μg/mL solution for thehigh dose group and 2 μg/mL solution for the low dose group.Dexmedetomidine was infused using a controlled infusion device. Thedexmedetomidine could be administered by a designated IV line fordexmedetomidine and could also be administered via a designated IV lineof dexmedetomidine attached to a Y-site adapter, or through a specifiedside port if given through a central line. No other medications were tobe bolused through the dexmedetomidine infusion line. The same syringeor bag used for the loading dose could be used for maintenance—only therate of infusion changed.

If rescue midazolam was necessary, the dexmedetomidine dose was titratedupwards and the need to administer additional midazolam was reassessedfollowing dexmedetomidine administration. If rescue pain medication wasnecessary, then fentanyl or morphine was administered after the subjectwas first treated with an increase in the dexmedetomidine infusion rate,at age-specific doses, or as a continuous infusion. Subjects receivingcontinuous infusions of fentanyl or morphine prior to randomizationcould continue these infusions throughout study drug administration ifrequired.

Prior to the start of drug infusion, a baseline score on the UMSS wasobtained. The UMSS scale is given in Table 12 below. If a loading dosewas administered, the UMSS score was obtained immediately before loadingand at 5 and 10 minutes during the loading dose. If the loading doseoccurred over 20 minutes, then the UMSS score was obtained at 15minutes. If no loading dose was administered, the UMSS score wasobtained at the start of the maintenance infusion and at 5, 10, 15, 30,and 60 minutes for the first hour. The UMSS score was obtained every 4hours during the remainder of the maintenance infusion. IF rescuemedication was administered, the UMSS score was measured immediatelybefore and 5 minutes after the rescue medication was administered. TheUMSS score was also obtained immediately before and 5 minutes after anon-pharmacological intervention, such as swaddling, cuddling, orrocking.

TABLE 12 University of Michigan Sedation Scale Clinical Score Level ofSedation 0 Awake/Alert 1 Minimally Sedated: Tired/sleepy, appropriateresponse to verbal conversation and/or sounds. 2 Moderately Sedated:Somnolent/sleeping, easily aroused with light tactile stimulation. 3Deeply sedated: Deep sleep, arousable only with significant physicalstimulation. 4 Unarousable

Chemistry, hematology and urinalysis samples were obtained for thelaboratory tests. A baseline cortisol level test was conducted prior tothe start of dexmedetomidine administration. For CPB subjects, thisblood draw was obtained postoperatively within 90 minutes following thestart of dexmedetomidine. An ACTH-stimulation test were performed at theconclusion of dexmedetomidine infusion.

Safety measures included collection of adverse events (adverse events),heart rate (HR in beats per minute [bpm]), systolic blood pressure (SBPin millimeters of mercury [mmHg]), diastolic blood pressure (DBP inmillimeters of mercury [mmHg]), mean arterial pressure (MAP inmillimeters of mercury [mmHg]), oxygen saturation by pulse oximetry(SpO₂ in percentage), and respiratory rate (RR in breaths/minute[breaths/min]) or ventilator settings, laboratory results, andelectrocardiogram (ECG) monitoring.

The statistical analyses were performed using SAS™ Statistical SoftwareSystem (SAS Institute, Inc., Cary, N.C.), version 9.1. All statisticaltests were 2 sided and p values ≤0.0500, after rounding to 4 decimalplaces, were considered statistically significant unless otherwisespecified. In general, missing data were not imputed. For continuousvariables, N, mean, median, SD, minimum, Q1, Q3 and maximum arepresented. The mean and median was displayed to 1 decimal place morethan the raw value. The standard deviation (SD) is displayed to 2decimal places more than the raw value. For categorical variables, N andpercent is shown. All percentages were reported to 1 decimal place.

Exposure to dexmedetomidine was highest in the high dose and generallygreater in the other diagnoses group. The average maintenance dose ofdexmedetomidine in μg/kg/hr in the low dose was 0.33 μg/hr/hr with s/pCPB subjects requiring slightly less maintenance infusion to maintaintarget sedation. Similarly, in the high dose dexmedetomidine group themaintenance infusion averaged 0.59 μg/kg/hr, with s/p CPB subjectsrequiring less maintenance infusion. The median duration of maintenanceinfusion was 1215.0 minutes (20.3 hours) for the low dose group and1127.5 minutes (18.8 hours) for the high dose group. Median totalloading dose was higher for subjects ASA class P3 and P4 than P1 and P2.The median total maintenance dose was similar for ASA Class P1 and P2,and P3 and P4 subjects. The median exposure to dexmedetomidine is givenin Table 13 below. The time of exposure is given in Table 14 below.

TABLE 13 Median Exposure to Study Drug by Time Points Group 1 Low DoseGroup 2 High Dose s/p CPB Other Dx s/p CPB Other Dx dexmedetomidinedexmedetomidine dexmedetomidine dexmedetomidine Median Parameter - dosedose Total dose dose Total Age Groups Combined N = 36 N = 53 N = 89 N =37 N = 49 N = 86 Loading dose N 11 19 30 12 20 32 Total loading 2.402.55 2.48 3.59 4.50 4.14 dose (μg) Duration (min) 10.0 10.0 10.0 15.017.5 17.5 Loading dose; ASA Class: PI and P2 N 3 7 10 2 7 9 Totalloading 1.70 2.55 2.20 5.75 3.60 3.60 dose (μg) Duration (min) 10.0 10.010.0 15.0 10.0 10.0 Loading dose; ASA Class: P3 and P4 N 8 12 20 10 1323 Total loading 2.78 2.78 2.78 3.38 4.80 4.50 dose (μg) Duration (min)10.0 10.0 10.0 15.0 20.0 20.0 Maintenance dose N 36 53 89 37 49 86Average maintenance 0.30 0.35 0.33 0.52 0.67 0.59 dose (μg/kg/hr) Totalmaintenance 48.67 44.85 45.93 68.60 143.81 76.56 dose (μg) Duration(min) 1114.5 1380.0 1215.0 840.0 1252.0 1127.5 Maintenance dose: ASAClass P1 and P2 N 9 22 31 5 16 21 Average maintenance 0.33 0.35 0.340.55 0.64 0.59 dose (μg/kg/hr) Total maintenance 49.20 52.63 52.14 81.74162.79 115.21 dose (μg) Duration (min) 1110.0 1287.5 1215.0 790.0 1374.51225.0 Maintenance dose: ASA Class P3 and P4 N 27 31 58 32 33 65 Averagemaintenance 0.30 0.35 0.32 0.51 0.67 0.57 dose (μg/kg/hr) Totalmaintenance 48.15 42.39 42.91 59.27 112.75 74.67 dose (μg) Duration(min) 1119.0 1430.0 1264.0 975.0 1159.0 1120.0

TABLE 14 Time of Exposure Group 1 Low Dose Group 2 High Dose s/p CPBOther Dx s/p CPB Other Dx dexmedetomidine dexmedetomidinedexmedetomidine dexmedetomidine Median Parameter - dose dose Total dosedose Total Age Groups Combined N = 36 N = 53 N = 89 N = 37 N = 49 N = 86Time of exposure <1 hour N 1 1 Total dose (μg) — — — — 7.25 7.25 47.047.0 Time of exposure >1 hour N 36 53 89 37 48 85 Average maintenance0.30 0.35 0.33 0.52 0.67 0.59 dose (μg/kg/hr) Total dose (μg) 48.6746.31 46.85 68.60 146.90 79.44 Duration (min) 1121.0 1390.0 1215.0 848.01288.5 1133.0 Time of exposure >6 hours N 31 49 80 30 45 75 Averagemaintenance 0.31 0.35 0.33 0.52 0.67 0.59 dose (μg/kg/hr) Totalmaintenance 50.69 51.49 50.97 78.49 172.80 88.26 dose (μg) Duration(min) 1160.0 1415.0 1343.5 1050.5 1320.0 1170.0 Time of exposure >12hours N 26 39 65 23 41 64 Average maintenance 0.31 0.35 0.33 0.54 0.660.60 dose (μg/kg/hr) Total maintenance 53.67 59.71 56.09 86.24 172.80112.82 dose (μg) Duration (min) 1307.5 1439.0 1411.0 1142.0 1395.01266.0 Time of exposure 0-6 hours N 5 4 9 7 4 11 Average maintenance0.23 0.39 0.30 0.49 0.63 0.56 dose (μg/kg/hr) Total dose (μg) 11.99 9.3111.16 25.67 30.16 28.57 Duration (min) 357.0 147.5 353.0 360.0 305.0360.0 Time of exposure >6-12 hours N 5 10 15 7 4 11 Average maintenance0.33 0.34 0.33 0.50 0.96 0.56 dose (μg/kg/hr) Total dose (μg) 25.9041.49 36.55 31.59 106.61 34.19 Duration (min) 470.0 438.0 466.0 533.0542.5 533.0

Overall the high dose dexmedetomidine group was clinically bettersedated than the low dose dexmedetomidine groups with 54.3% of high dosesubjects not requiring rescue midazolam compared to 44.6% in the lowdose dexmedetomidine groups, although this was not statisticallysignificant (p=0.2751). By age, a smaller percentage of subjects in agegroup II did not require rescue midazolam for sedation in comparisonwith age group I in both dexmedetomidine dose groups; this differencewas not statistically significant (p=0.6723). In both dose groupssubjects undergoing open heart surgery with CPB received more rescuemidazolam than those in the other diagnoses groups. The greatestdifference between treatment groups was in the heart surgery subjectswith more subjects in both age groups receiving high dosedexmedetomidine than low dose dexmedetomidine and not requiringmidazolam sedation rescue. The difference was 22.73%, although it wasnot statistically significant (p=0.0974). Table 15 contains number andpercent of subjects who did not require midazolam for sedation duringtreatment. Table 16 contains the differences between treatment groups inpercentage of subjects who did not require midazolam for sedation duringtreatment.

TABLE 15 Number and Percent of Subjects Who Did Not Require RescueMidazolam for Sedation During the Treatment Period While Intubated s/pCPB Other Dx s/p CPB Other Dx Number and Percent of dexmedetomidinedexmedetomidine dexmedetomidine dexmedetomidine Subjects^(a) dose doseTotal dose dose Total Total ASA Class N = 33 N = 50 N = 83 N = 34 N = 47N = 81 Age Group I^(b) 5 (15.2) 20 (40.0) 25 (30.1) 10 (29.4)  20(42.6)  30 (37.0) Age Group II^(c) 4 (12.1)  8 (16.0) 12 (14.5) 7 (20.6)7 (14.9) 14 (17.3) Total 9 (27.3) 28 (56.0) 37 (44.6) 17 (50.0)  27(57.4)  44 (54.3) ASA Class: P1, P2 N = 8  N = 21 N = 29 N = 5 N = 16 N= 21 Age Group I^(b) 1 (12.5)  8 (38.1)  9 (31.0) 1 (20.0) 7 (43.8)  8(38.1) Age Group II^(c) 0  4 (19.0)  4 (13.8) 0 2 (12.5) 2 (9.5) Total 1(12.5) 12 (57.1) 13 (44.8) 1 (20.0) 9 (56.3) 10 (47.6) ASA Class: P3, P4N = 25 N = 29 N = 54 N = 29 N = 31 N = 60 Age Group I^(b) 4 (16.0) 12(41.4) 16 (29.6) 9 (31.0) 13 (41.9)  22 (36.7) Age Group II^(c) 4 (16.0) 4 (13.8)  8 (14.8) 7 (24.1) 5 (16.1) 12 (20.0) Total 8 (32.0) 16 (55.2)24 (44.4) 16 (55.2)  18 (58.1)  34 (56.7) ^(a)Number and percent ofsubjects who did not require rescue midazolam for sedation based onachieving and maintaining a target UMSS range of 1 to 3 while intubated.^(b)Age group I = ≥1 month to <24 months ^(c)Age group II = ≥24 monthsto <17 years old

TABLE 16 Differences Between Treatment Groups in Percentage of Subjectswho did not Require midazolam for Sedation During the Treatment PeriodWhile Intubated Underlying Condition/Age Group 1 Low Group 2 HighDifference Group Dose Dose (Group 1 − 2)^(b) p-value^(c) Total ASA ClassAll Diagnoses [n (%)]^(a) 37/83 (44.6) 44/81 (54.3) −9.74 0.2751 AgeGroup I^(d) 25/57 (43.9) 30/56 (53.6) −9.71 0.3984 Age Group II^(e)12/26 (46.2) 14/25 (56.0) −9.85 0.6723 s/p CPB [n (%)]  9/33 (27.3)17/34 (50.0) −22.73 0.0974 Age Group I^(d)  5/22 (22.7) 10/23 (43.5)−20.75 0.2461 Age Group II^(e)  4/11 (36.4)  7/11 (63.6) −27.27 0.3938Other Diagnoses [n (%)]    28/50 (56.0%)    27/47 (57.4%) −1.45 1.0000Age Group I^(d) 20/35 (57.1) 20/33 (60.6) −3.46 0.9653 Age Group II^(e) 8/15 (53.3)  7/14 (50.0) 3.33 1.0000 ASA Class: P1, P2 All Diagnoses [n(%)]^(a) 13/29 (44.8) 10/21 (47.6) −2.79 1.0000 Age Group I^(d)  9/19(47.4)  8/15 (53.3) −5.96 1.0000 Age Group II^(e)  4/10 (40.0)  2/6(33.3) 6.67 1.0000 s/p CPB [n (%)]  1/8 (12.5)  1/5 (20.0) −7.50 1.0000Age Group I^(d)  1/6 (16.7)  1/3 (33.3) −16.67 1.0000 Age Group II^(e)0/2 0/2 0.00 — Other Diagnoses [n (%)] 12/21 (57.1)  9/16 (56.3) 0.891.0000 Age Group I^(d)  8/13 (61.5)  7/12 (58.3) 3.21 1.0000 Age GroupII^(e)  4/8 (50.0)  2/4 (50.0) 0.00 1.0000 ASA Class: P3, P4 AllDiagnoses [n (%)]^(a) 24/54 (44.4) 34/60 (56.7) −12.22 0.2645 Age GroupI^(d) 16/38 (42.1) 22/41 (53.7) −11.55 0.4228 Age Group II^(e)  8/16(50.0) 12/19 (63.2) −13.16 0.6594 s/p CPB [n (%)]  8/25 (32.0) 16/29(55.2) −23.17 0.1515 Age Group I^(d)  4/16 (25.0)  9/20 (45.0) −20.000.3722 Age Group II^(e)  4/9 (44.4)  7/9 (77.8) −33.33 0.3336 OtherDiagnoses [n (%)] 16/29 (55.2) 18/31 (58.1) −2.89 1.0000 Age Group I^(d)12/22 (54.5) 13/21 (61.9) −7.36 0.8573 Age Group II^(e)  4/7 (57.1) 5/10 (50.0) 7.14 1.0000 ^(a)Subjects who did not require rescuemidazolam for sedation based on achieving and maintaining a target UMSSrange 1-3 while intubated. ^(b)Mean difference between treatment groupsin percentage of subjects who did not require rescue midazolam forsedation based on achieving and maintaining a target UMSS of 1-3 whileintubated. ^(c)P-value for risk difference for 2 × 2 table fromChi-Square test with continuity correction. ^(d)Age group I = ≥1 monthto <24 months ^(e)Age group II = ≥24 months to <17 years old

All age groups and diagnoses receiving the high dose of dexmedetomidinewere in the targeted UMSS range 87.8 to 99.2% of the time compared to85.5 to 99.0% of the time in the low dose dexmedetomidine groups. Therewere no statistical differences between dexmedetomidine dose groups inthe absolute time or percentage of time subjects were in the targetsedation range (UMSS 1-3). All age groups and diagnoses receiving thelow dose of dexmedetomidine were out of the target UMSS range 1.0 to14.5% of the time compared to 0.8 to 12.2% of the time in the high dosedexmedetomidine groups. There were no statistical differences betweendexmedetomidine dose groups in the absolute time or percentage of timesubjects were out of the target sedation range (UMSS <1 or >3).

Overall, more rescue midazolam for sedation (total dose and dose/kg) wasrequired in the low dose dexmedetomidine groups than the high dosedexmedetomidine groups, although the differences were not statisticallysignificant. With the age groups combined, 46/83 subjects (55.4%) in thelow dose dexmedetomidine group required rescue midazolam for sedationcompared with 37/81 subjects (45.7%) in the high dose dexmedetomidinegroup. Median total amount of rescue midazolam required for sedationwhile intubated during the treatment period for the subjects thatrequired rescue midazolam for sedation was 1.965 mg (range: 0.19-30.80mg) in the low dose group and 2.00 mg [range: 0.10-13.20 mg]) the highdose group; and median amount of rescue midazolam per kg was 0.266 mg/kg(range: 0.02-1.49 mg/kg) in the low dose group and 0.179 mg/kg (range:0.02-1.11 mg/kg) in the high dose group. Results were similar by agegroup.

With the age groups combined, 53/83 subjects (63.9%) in the low dosedexmedetomidine group and 44/81 subjects (54.3%) in the dexmedetomidinehigh dose dexmedetomidine group received rescue fentanyl for analgesiawhile intubated during the treatment period. Median total amount ofrescue fentanyl required for analgesia for the subjects who requiredrescue fentanyl was 46.00 μg (range: 1.50-593.00 μg) in the low dosegroup and 35.13 μg (range: 1.50-750.00 μg) in the high dose; and medianamount per kg of rescue fentanyl required for analgesia was 4.13 μg/kg(range: 0.10-83.52 μg/kg) in the low dose group and 3.25 μg/kg (range:0.08-35.98 μg/kg) in the high dose group.

With the age groups combined, 35/83 subjects (42.2%) in the low dosegroup and 32/81 subjects (39.5%) in the dexmedetomidine high dose groupreceived rescue morphine for analgesia while intubated during thetreatment period. Median total amount of rescue morphine required foranalgesia for the subjects who required rescue morphine was 1.80 mg(range: 0.25-20.50 mg) in the low dose dexmedetomidine group and 1.63 mg(range: 0.32-15.00 mg) in the high dose dexmedetomidine group; andmedian amount of rescue morphine per kg was 0.20 mg/kg (range: 0.03-4.10mg/kg) in the low dose dexmedetomidine group and 0.17 mg/kg (range:0.05-0.57 mg/kg) in the high dose dexmedetomidine group. Difference intime to first rescue medication was not statistically significant;median time from start of dexmedetomidine infusion to first dose ofrescue medication was 1.6 hours (95% CI: 0.93, 3.38) in the low dosedexmedetomidine group and 2.0 hours (95% CI: 1.07, 3.75) in the highdose group.

The time to extubation was estimated from the first termination ofmechanical ventilation within the dexmedetomidine infusion period untilthe 24-hour follow-up. If the subject's ventilator setting was notavailable, and dexmedetomidine was discontinued because it was no longerrequired for sedation, extubation time was estimated as the end ofdexmedetomidine date/time. Subjects with no measurable time toextubation as described above were excluded from analysis. If extubationwas successful, the subject was considered to have the event. Subjectswho were not extubated were censored; time of censoring was set to thetime of the subject's last observation during the correspondingevaluable period and might represent time of subject's withdrawal fromthe study, time of death, or the time of the last recorded observationduring the evaluable period, whichever happened first. Median time tosuccessful extubation was 23.8 hours (95% CI: 18.55, N/A) in the lowdose dexmedetomidine group and 20.5 hours (95% CI: 17.13, 23.33) in thehigh dose dexmedetomidine group; the difference was not statisticallysignificant.

In general, moderate or severe adverse events were more common in thelow dose than high dose dexmedetomidine groups and there were moreactual events reported in age group I than age group II: in age group I,moderate and severe treatment-related adverse events were experienced by17 (27.0%; 30 events) and 10 subjects (16.7%; 17 events) in the low andhigh dose groups, respectively; and in age group II, moderate and severetreatment-related adverse events were experienced by 8 (30.8%; 13events) and 6 subjects (23.1%; 9 events) in the low and high dosegroups, respectively. Overall, 5/175 subjects (2.9%) reported a total ofseven severe treatment-related adverse events; all severetreatment-related adverse events were reported in the low dosedexmedetomidine groups. The severe treatment-related adverse eventsreported were myocarditis, pyrexia, status epilepticus, dyspnea,ventricular fibrillation, chest pain, and wheezing. The severemyocarditis event was also considered a serious treatment-relatedadverse event.

Treatment-related adverse events experienced by 2 or more subjects in adose group in age group I were hypotension (3 subjects [4.8%] and 5subjects [8.3%], in the low and high dose dexmedetomidine groups,respectively), agitation (2 [3.2%] and 4 [6.7%]), and bradycardia (2[3.2%] and 2 [3.3%]), and hypertension (2 [3.2%] in the low dosedexmedetomidine group); and in age group II, hypotension (2 subjects[7.7%] in the high dose group).

Serious treatment-related adverse events and treatment-related adverseevents that led to dexmedetomidine or study discontinuation were onlyreported in age group I. Two serious treatment-related adverse eventswere reported in this study, myocarditis (1 subject, low dose) and apnea(1 subject, high dose); both events were considered possibly or probablyrelated to dexmedetomidine. Seven subjects (4.0%) experienced a total of8 treatment-related adverse events that led to discontinuation ofdexmedetomidine (respiratory rate decreased and respiratory acidosis[each 1 subject, low dose] and bradycardia, device electrical finding,endotracheal intubation complication, agitation, apnea, hypotension[each 1 subject, high dose]). Two subjects experienced treatment-relatedadverse events that led to study discontinuation (oxygen saturationdecreased and agitation [1 subject, high dose] and hypotension [1subject, low dose]). There were 4 deaths, all unrelated todexmedetomidine. No subjects stopped dexmedetomidine due to death.

Whereas the median amount (total and per kg) of rescue midazolam forsedation and rescue fentanyl and morphine was not statisticallysignificantly different between the low and high dose dexmedetomidinegroups, total and per/kg doses of rescue midazolam for sedation, rescuefentanyl for analgesia, and rescue morphine for analgesia trended higherin the low dose dexmedetomidine group.

The study demonstrates that dexmedetomidine was clinically effective atsedating critically ill, initially intubated infants and childrenfollowing major cardiac surgery with CPB and non-cardiac surgery. Therewas a non-significant (p=0.2751) dose-response effect observed with moresubjects (54.3%) in the high dose dexmedetomidine groups not requiringrescue midazolam to maintain the target sedation than in the low dosedexmedetomidine groups (44.6%), irrespective of age. High dosedexmedetomidine was most effective in the heart surgery subjects (s/pCPB) with more subjects of both age groups who received high dosedexmedetomidine than low dose dexmedetomidine not requiring midazolamsedation rescue (p=0.0974, difference=22.73%). All age groups anddiagnoses receiving the high dose of dexmedetomidine were in the targetUMSS range (1-3) 87.8 to 99.2% of the time compared to 85.5 to 99.0% ofthe time in the low dose dexmedetomidine groups; the difference was notstatistically significant.

Example 3: Pharmacokinetics of Dexmedetomidine in Pediatric Patients

The present study characterizes the pharmacokinetic and pharmacodynamicprofile of dexmedetomidine administered as an intravenous (IV) loadingdose followed by a continuous IV infusion in pediatric subjects.

A 56-subject, open-label, multicenter, escalating dose study ofdexmedetomidine was conducted on initially intubated and mechanicallyventilated pediatric subjects who required sedation in an intensive caresetting and was anticipated to require a minimum of 6 hours but not toexceed 24 hours of continuous IV sedation. The present studyinvestigated the pharmacokinetics and pharmacodynamics ofdexmedetomidine. The subjects were at least 2 years old and less than 17years old.

The subjects were separated into two age groups. Group I consisted ofchildren who were at least 2 years old and younger than 6 years old andGroup II consisted of children who were at least 6 years old and youngerthan 17 years old. Within each group there were four escalating dosinglevels (Table 17). The subject disposition and demographics of the studyare described in Table 18.

A total of 69 subjects were enrolled into the study. Of those, 59received dexmedetomidine (any amount) and were included in the safetypopulation (26 in Group I, 33 in Group II).

A total of 56 subjects completed the study, 26 in Group I and 30 inGroup II. Three patients from Group II were prematurely discontinuedfrom the study due to protocol deviations (1 subject each from DoseLevels 1, 2 and 3).

The full evaluable population consisted of 57 subjects who received thestudy drug infusion for at least 5 hours (26 in Group I, 31 in GroupII). Two subjects from Group II were excluded from the full evaluablepopulation.

Subjects in Group I were primarily male (57.7%) and White (88.5%) with amean (SD) age of 3.7 (1.12) years. Subjects in Group II were primarilyfemale (63.6%) and White (72.7%) with a mean (SD) age of 10.3 (3.24)years, as shown in Table 18.

TABLE 17 Study Design Group I (Ages ≥2 Maintenance through <6 years old)Loading Infusion (at Post- Group II (Ages ≥6 Dose (10 least 6 hours andTreatment through <17 years old) minutes) up to 24 hours) Period Level 10.25 μg/kg 0.2 μg/kg/hr 24 hours Level 2 0.50 μg/kg 0.4 μg/kg/hr 24hours Level 3 1.00 μg/kg 0.7 μg/kg/hr 24 hours Level 4 1.00 μg/kg 2.0μg/kg/hi 24 hours Abbreviations: DEX = dexmedetomidine

TABLE 18 Subject Demographics-Safety Population Group I Group II DoseDose Dose Dose Dose Dose Dose Dose Characteristic Level 1 Level 2 Level3 Level 4 Level 1 Level 2 Level 3 Level 4 Mean (SD) (N = 8) (N = 6) (N =6) (N = 6) (N = 8) (N = 8) (N = 9) (N = 8) Age (years)  3.4 (1.03) 3.6(0.98)  4.3 (1.50)  3.6 (0.96) 9.3 (2.23) 10.4 (3.99) 11.1 (3.64) 10.4(3.15) % Male 50.0  50.0 66.7 66.7 25.0 37.5 22.2 62.5 % White 87.5100.0 83.3 83.3 62.5 75.0 88.9 62.5 Weight (kg) 14.6 (3.02) 13.8 (3.55) 16.5 (4.55) 13.7 (1.75) 40.5 (28.65)  32.6 (17.42)  37.1 (24.42)  38.5(19.36) height (cm) 96.6 (6.35) 94.8 (10.42) 101.5 (10.31) 101.2 (12.64)131.8 (17.71)  133.6 (23.57) 132.4 (18.99) 138.1 (25.52) Abbreviations:DEX = dexmedetomidine

HCl injection (manufactured and supplied by Hospira, Inc.).Dexmedetomidine hydrochloride (HCl) injection (100 μg/mL, base) wassupplied to the investigative sites for infusion. Study medication wasprepared (diluted) by the site pharmacy to 4 μg/mL in 0.9% sodiumchloride and was not refrigerated. The dexmedetomidine was administeredas a two-stage IV infusion using a controlled infusion device through adesignated IV line, but never directly into the pulmonary artery.

Dexmedetomidine was administered as a two-stage IV infusion with aloading dose infusion for 10 minutes and was immediately followed by acontinuous fixed maintenance dose for a minimum of 6 to a maximum of 24hours, at four increasing dose levels. Each dose increase was dependenton the tolerability of the previous dose. After the subjects completedthe dexmedetomidine maintenance infusion, the post-infusion procedureswere initiated and continued for 24 hours.

The primary evaluation was the estimation of dexmedetomidinepharmacokinetic parameters for each age group by dose level includingAUC (area under the plasma concentration-time curve), C_(max) (observedpeak plasma concentration), C_(ss) (steady state concentration), CL(plasma clearance), V_(ss) (volume of steady state distribution) andt_(1/2) (terminal half-life).

Safety monitoring included treatment emergent adverse events (TEAEs)(severity, relationship to study drug), vital signs, clinical laboratoryresults and electrocardiogram (ECG) and physical exam finding.

The dexmedetomidine infusion began after discontinuation of all othersedative and analgesic agents and the subject attained a Ramsay SedationScale (RSS) of 2, 3, or 4. The RSS is a clinically derived scale used toquantify depth of anesthesia and has been used in children ranging inage from 1 month to 18 years old. The RSS scale is given in Table 19below. Rescue medication (midazolam or fentanyl) was administered asneeded for sedation and pain, respectively, during study drugadministration based on results of the sedation (RSS) and pain (Face,Legs, Activity, Cry, and Consolability [FLACC]) scales. After thediscontinuation of dexmedetomidine infusion, further sedation andanalgesia was provided per standard of care.

TABLE 19 Ramsay Sedation Scale Clinical Score Level of Sedation 1Patient is anxious and agitated or restless, or both. 2 Patient iscooperative, orientated and tranquil. 3 Patient responds to commandonly. 4 Patient exhibits brisk response to light glabellar (between theeyebrows) tap or loud auditory stimulus. 5 Patient exhibits a sluggishresponse to light glabellar tap or loud auditory stimulus. 6 Patientexhibits no response to stimulus.

The level of sedation was assessed first using the RSS and then theRichmond Agitation Sedation Scale (RASS) immediately after completion ofthe RSS. The RASS has been used and validated to quantify depth ofanesthesia in adults in the ICU setting; however it has not beenvalidated in infants and children. The purpose of using the RASS in thisstudy was to evaluate the suitability of the RASS in children who were 2years old to younger than 17 years old. The RASS scale is given in Table20 below.

TABLE 20 Richmond Agitation Sedation Scale (RASS) Score Term Description+4 Combative Overtly combative, violent, immediate danger to staff +3Very agitated Pulls or removes tube(s) or catheter(s); aggressive +2Agitated Frequent non-purposeful movement, fights ventilator +1 RestlessAnxious but movements not aggressive, vigorous 0 Alert and calm −1Drowsy Not fully alert, but has sustained awakening (eye-opening/eyecontact) to voice (>10 seconds) −2 Light Sedation Briefly awakens witheye contact to voice (<10 seconds) −3 Moderate Movement or eye openingto voice (but no eye Sedation contact) −4 Deep Sedation No response tovoice, but movement or eye opening to physical stimulation. −5Unarousable No response to voice or physical stimulation

Based on the RSS and RASS scores and clinical judgment, additionalrescue sedation with IV midazolam was administered if subjects were notcompletely sedated. For subjects 6 months to 5 years old, the midazolamdose was 0.05 to 0.1 mg/kg. For subjects 6 to 12 years old, themidazolam dose was 0.025 to 0.05 mg/kg. Subjects who were older than 12years were administered 1 mg/kg of midazolam.

Pain was assessed using the Faces, Legs, Activity, Cry, andConsolability (FLACC) scale. The FLACC scale is a valid and reliableobservational tool used as a measure of pain in children ranging in agefrom 2 months to 18 years old. The FLACC scale is given in Table 21below.

TABLE 21 Faces, Legs, Activity, Cry, and Consolability Scale ScoringCategory 0 1 2 Face No particular Occasional Frequent to expressiongrimace or frown, constant or smile withdrawn, quivering chin,disinterested clenched jaw Legs Normal position Uneasy, restless,Kicking, or legs or relaxed tense drawn up Activity Lying quietly,Squirming, Arched, rigid, normal position, shifting back or jerkingmoves easily and forth, tense Cry No cry (awake Moans or whimpers;Crying steadily, or asleep) occasional screams or sobs, complaintfrequent complaints Con- Content, Reassured by Difficult to solabilityrelaxed occasional console touching, hugging or comfort or being talkedto, distractible

Rescue fentanyl IV was administered at the recommended dose of 0.25 to 1μg/kg as needed to treat pain based on clinical judgment or FLACC scoresgreater than 4 while receiving dexmedetomidine infusion. FLACC scoreswere documented before and within five minutes after the administrationof any rescue fentanyl. Each of the five FLACC scale categories wasscored from 0 to 2, which resulted in a total score between zero andten.

Prior medications, defined as medications taken within 48 hours prior tothe start of study drug infusion, were taken by 96.6% of the studysubjects. The most frequently used prior medications reported for use bysubjects were from the nervous system (94.9%), alimentary tract andmetabolism (83.1%), and musculoskeletal system (79.7%) drug classes andincluded the following: fentanyl citrate (81.4%), midazolam (66.1%),magnesium sulfate (28.8%), ranitidine (28.8%), and vecuronium (27.1%).

Concomitant medications were defined as infusion and noninfusionmedications received during the study drug infusion period through thepost-study drug administration period. Concomitant noninfusionmedications were taken by all subjects (100%) and infusion medicationswere taken by 39.0% of subjects in the enrolled population. The mostfrequently used concomitant noninfusion medications reported were fromthe nervous system (100%), alimentary tract and metabolism (98.3%), andantiinfectives for systemic use (96.6%) drug class and included thefollowing: fentanyl citrate (88.1%), midazolam (67.8%), magnesiumsulfate (35.6%), and cephalothin (32.2%). The most frequently usedconcomitant infusion medications reported were from the cardiovascularsystem (30.5%), blood and blood forming organs (28.8%), nervous system(23.7%), and alimentary tract and metabolism (22.0%) drug class andincluded the following: milrinone (23.7%), papaverine (20.3%), heparin(18.6%), fentanyl citrate (6.8%), and midazolam (5.1%).

Subjects receiving continuous IV infusions of fentanyl were able to havethese infusions re-started after starting the dexmedetomidine infusion.Subjects who were receiving continuous infusions of fentanyl had FLACCscores recorded immediately before and within five minutes after anychange in the dose of the fentanyl infusion.

The subjects had to be initially intubated when starting thedexmedetomidine treatment. Once subjects had met site-specifiedrespiratory criteria, they could undergo tracheal extubation, at anytime following the start of the loading dose. The dexmedetomidineinfusion could be continued during and after the extubation process.Sedation levels and vital signs were monitored and recorded in theperi-extubation period.

The pharmacodynamic and safety measures monitored included: sedationlevels (by RSS and RASS scores), heart rate (HR), blood pressure (BP),respiratory rate (RR), and oxygen saturation by pulse oximetry (SpO₂).The BP, HR, SpO2, and RR were recorded prior to the loading dose, at 5and 10 minutes during the load, and hourly during the maintenanceinfusion, as close as possible (up to 5 minutes prior) to the scheduledpharmacokinetic sampling times, and concurrent with the RSS, RASS, andthe FLACC scale. Cardiac monitoring was continuous. A 12-lead ECG wasobtained after five hours of maintenance infusion but beforediscontinuing the infusion. After discontinuing the infusion, HR, BP,RR, and SpO₂ were recorded every 15 minutes for the first hour, every 30minutes for 2 hours, every hour for 3 hours and then every 4 hours untillast pharmacokinetic sample was obtained. Vital signs were obtained inconjunction with the pharmacokinetic samples, up to five minutes prior.

The dexmedetomidine infusion rate was not titrated during this trial.After the discontinuation of the dexmedetomidine infusion, furthersedation and analgesia may have been provided per standard of care;however, dexmedetomidine was not restarted until after the lastpharmacokinetic sample was obtained.

Venous or arterial blood samples were collected for determination ofplasma dexmedetomidine concentrations. Blood samples were collected viaa peripheral venous, central venous, peripherally inserted centralvenous catheter (PICC) or arterial line into heparinized vacutainertubes for pharmacokinetic analysis. An arterial line must have alreadybeen in place as part of the standard of care in order to have been usedfor sample collection. In no case was an arterial line placed for thesole reason of collection of pharmacokinetic samples. Additionally, allpharmacokinetic samples were drawn consistently from either a venous oran arterial access for the duration of the study; interchangeabilitybetween venous and arterial draws was not allowed. Blood samples werecollected at each of the following time points: no more than 30 minutesprior to the start of the loading dose; within five minutes before theloading dose was finished and simultaneous with the start of themaintenance infusion; 0.5, 1, 2 and 4 to 6 hours after the start ofmaintenance infusion; within 30 minutes prior to the end of maintenanceinfusion, which must have been within 24 hours of start of maintenanceinfusion; ten minutes after the maintenance infusion had ended; and 0.5,1, 2, 4 and 10 hours after the maintenance infusion had ended.

For pharmacokinetic analyses, venous blood samples (1 mL) were collectedin heparinized tubes at a site opposite from the site of infusion (e.g.,left arm vs. right arm). Samples were not drawn from the second lumen ofa multi-lumen catheter through which drug was being administered. Ifarterial blood samples (1 mL) were collected, heparinized tubes werealso used.

The pharmacokinetic analysis was performed using model independentmethods. The primary evaluation was the assessment of dexmedetomidinepharmacokinetics on the full evaluable population. As used herein, theterm “full evaluable population” refers to the pediatric subjects whoreceived at least 5 hours of dexmedetomidine infusion. As used herein,the term “safety population” refers to the pediatric subjects whoreceived any amount of dexmedetomidine.

Pharmacokinetic parameters were estimated by non-compartmental methods.Parameters estimated included: AUC (area under the plasmaconcentration-time curve), C_(max) (observed peak plasma concentration),CL (plasma clearance), C_(ss) (steady state concentration), V_(ss)(volume of steady state distribution), and t_(1/2) (terminal half-life).

Additional parameters were determined as deemed appropriate. Plasmaconcentrations and resultant pharmacokinetic parameters were summarizedby descriptive statistics, number of subjects, arithmetic mean, SD,coefficient of variation (CV), median, and range (minimum and maximum).

An assessment of dose proportionality was made for AUC and C_(max) amongthe dose levels administered. The Power Analysis approach and datavisualization techniques were used for this assessment.

The primary evaluation was the assessment of dexmedetomidinepharmacokinetics. The pharmacokinetic analyses were summarized for eachage group by dose level for the full evaluable population, as a primaryanalysis. Data from all full evaluable subjects were included in theanalysis. The pharmacokinetic parameters were estimated bynon-compartmental methods. Summary statistics for the pharmacokineticparameters were tabulated. Only subjects with sufficient pharmacokineticand pharmacodynamic data to calculate the pharmacokinetic andpharmacodynamic parameters were included in the analysis population.

In order to identify pharmacokinetic variation among different dosinglevels and different age groups, plots of mean plasma dexmedetomidineconcentrations vs. time curve during the study drug infusion period andpost-study drug infusion by dose level were produced for each age group.An overlay plot of individual plasma dexmedetomidine concentrations vs.time by dose level was generated. Descriptive statistics of C_(ss),C_(max), V_(ss), CL, AUC, t_(1/2), time of maximum concentration(t_(max)), terminal elimination rate constant (λz), volume ofdistribution (V_(d)), and weight-adjusted CL and V_(d) were summarizedby dose level for each age group. Within each dose level, a 2-samplet-test was used to assess the difference of these pharmacokineticparameters between age groups. The overall dose level by age group wasassessed with a 2-way analysis of variance. In addition, V_(ss) and CLwere also summarized by pooling data from all dose levels within eachage group, and a 2-sample t-test was used to assess the differencebetween age groups.

Scatter plots of V_(ss) and CL vs. age (yrs) and V_(ss) and CL vs.weight (kg) were visually produced with data pooled from all dose levelsand age groups. The association between these pharmacokineticparameters, adjusted for weight or dose, was assessed by linear ornon-linear regression analysis based on the results from the doseproportionality analysis.

The pharmacodynamic analyses were summarized for each age group by doselevel for the full evaluable population, as a primary analysis, and forthe safety population, as a secondary analysis. The followingdescriptive statistics were summarized by dose level for each age group:RSS₅, RSS_(avg), N (%) of subjects who received rescue midazolam, timeto first use of rescue midazolam, total amount of rescue midazolam, N(%) of subjects who received rescue fentanyl, total amount of rescuefentanyl, N (%) of subjects who were converted to alternative sedativeor analgesic therapy, time to successful extubation, and change frombaseline in mean, maximum, and minimum values of HR, SBP, DBP, MAP, RR,SpO₂ during infusion and post-infusion. As used herein, the term“baseline” refers to just prior to loading of dexmedetomidine.

The following descriptive statistics were also summarized, respectively,for subjects who received dexmedetomidine alone and for subjects whoreceived dexmedetomidine with co-administration of midazolam orfentanyl: RSS₅, RSS_(avg), N (%) of subjects who were converted toalternative sedative or analgesic therapy, time to extubation, changefrom baseline in mean, max, and min values of HR, SBP, DBP, MAP, RR,SpO₂ during infusion and post-infusion. These analyses were performedfor each age group by pooling data from all dose levels within the agegroup.

In addition, the time to the first rescue medication for sedation andthe time to successful extubation were assessed with the Kaplan-Meiermethod. Treatment group comparison and/or subjects who receiveddexmedetomidine alone and subjects who received dexmedetomidine withco-administration of midazolam or fentanyl for successful extubationwere then assessed with log-rank and Wilcoxon tests.

The relationship between the level of sedation and plasma concentration,supplemental sedation requirements, and impact of dexmedetomidine alone,and with co-administration of midazolam or fentanyl, on sedation, HR,and BP was analyzed. Subsequent pharmacokinetic and pharmacodynamicrelationships and modeling were done to identify covariates that mayfurther explain inter-individual variability in the pharmacokinetic andpharmacodynamic parameters.

The statistical analyses, summary tables, and data listings wereperformed or prepared using SAS® software, Version 9.1. Pharmacokineticparameters were calculated using the computer program WinNonlin (Version5.1 or higher PharSight, Mountainview, Calif.).

Summaries of the percentages of subjects stratified by dose level andage group who were intubated and simultaneously received rescuemidazolam for sedation during the treatment period are presented inTable 22 for the full evaluable population. A summary of theweight-adjusted total amount of rescue medication (midazolam, fentanyl)required for sedation and analgesia while intubated during the treatmentperiod for the full evaluable population is shown in Table 23. A summaryof the total amount of rescue medication (midazolam, fentanyl) requiredfor sedation and analgesia while intubated during the treatment periodfor the full evaluable population is shown in Table 24. A smallerpercentage of subjects in Group II received rescue midazolam forsedation in comparison with Group I across all treatment groups in thefull evaluable population, except for in the Dose Level 4 treatmentgroup, (37.5% vs. 50.0%, 42.9% vs. 66.7%, 25.0% vs. 50.0%, and 25.0% vs.16.7% in the Dose Level 1, 2, 3, and 4 treatment groups, respectively,in Group II vs. Group I, respectively). The differences between agegroups in the number of subjects that received rescue midazolam were notstatistically significant in any of the treatment groups for both thefull evaluable and safety populations. For the safety populationoverall, there were no statistically significant differences betweendose level groups in the total amount of rescue medications required forsedation or analgesia in subjects while intubated.

TABLE 22 Summary of Percentage of Subjects Who Received Rescue Midazolamfor Sedation During Treatment Period While Intubated, Stratified by DoseLevel and Age Group - Full Evaluable Population Dose Dose Dose DoseParameter/ Level 1 Level 2 Level 3 Level 4 Statistics N = 16 N = 13 N =14 N = 14 P-value Group I n (%) 4 (50.0) 4 (66.7) 3 (50.0) 1 (16.7)0.2446^(b) Group II n (%) 3 (37.5) 3 (42.9) 2 (25.0) 2 (25.0) 0.5110^(b)Total Age 7 (43.8) 7 (53.8) 5 (35.7) 3 (21.4) — Group n (%) P-values for1.0000 0.5921 0.5804 1.0000 — Differences^(a) Overall — — — — 0.9997 CMHTest^(c) Raw Mean — — — — 1 Scores Differ DF Probability — — — — 0.3174Abbreviations: CMH = Cochran-Mantel-Haenszel; midazolam = midazolam^(a)Differences between age Groups I and II within each dose level usingFisher's exact test. ^(b)P-value of Cochran-Armitage trend test withinage group. ^(c)Overall Cochran-Mantel-Haenszel test with a strata agegroup. Note: Group I: Ages ≥2 through 6 years old; Group II: Ages ≥6through 17 years old. Note: Dose Level 1—Dex LD = 0.25/CD = 0.2 μg/kg/hrDose Level 2—Dex LD = 0.50/CD = 0.4 μg/kg/hr Dose Level 3—Dex LD =1.00/CD = 0.7 μg/kg/hr Dose Level 4—Dex LD = 1.00/CD = 2.00 μg/kg/hr

TABLE 23 Summary of Weight-Adjusted Total Amount of Rescue Medication(Midazolam, Fentanyl) Required for Sedation and Analgesia WhileIntubated During the Treatment Period - Full Evaluable Population. TotalAmount of Dose Level 1 Dose Level 2 Dose Level 3 Dose Level 4 RescueMedication DEX N = 16 DEX N = 13 DEX N = 14 DEX N = 14 P-value Midazolam(mg/kg)^(a) Mean (SD) 0.067 (0.1024) 0.087 (0.1646) 0.109 (0.2229) 0.045(0.1053) Median (Min, Max) 0 (0, 0.31) 0.028 (0, 0.60) 0 (0, 0.82) 0 (0,0.30) Wilcoxon 0.5766^(b) Median 0.3751^(b) Fentanyl (μg/kg)^(a) Mean(SD) 2.24 (2.114) 191.13 (668.890) 2.84 (5.572) 2.26 (2.601) Median(Min, Max) 1.91 (0, 8.0) 2.68 (0, 2417.0) 1.54 (0, 22.0) 1.75 (0, 8.0)Wilcoxon 0.6896^(b) Median 0.3471^(b) Abbreviations: CD = continuousdose; DEX = dexmedetomidine; LD = loading dose; MAX = maximum; midazolam= midazolam; Min = minimum Note: Dose Level 1—Dex LD = 0.25/CD = 0.2μg/kg/hr Dose Level 2—Dex LD = 0.50/CD = 0.4 μg/kg/hr Dose Level 3—DexLD = 1.00/CD = 0.7 μg/kg/hr Dose Level 4—Dex LD = 1.00/CD = 2.00μg/kg/hr ^(a)Descriptive statistics are computed based on total numberof subjects whether or not they used any amount of rescue medication forsedation during the treatment period while intubated, within each doselevel. ^(b)P-values from Proc NPAR1WAY for specified tests.

TABLE 24 Summary of Total Amount of Rescue Medication (Midazolam,Fentanyl) Required for Sedation and Analgesia While Intubated During theTreatment Period - Full Evaluable Population. Total Amount of Dose Level1 Dose Level 2 Dose Level 3 Dose Level 4 Rescue Medication DEX N = 16DEX N = 13 DEX N = 14 DEX N = 14 P-value Midazolam (mg)^(a) Mean (SD)1.292 (1.8682) 1.369 (2.3948) 2.141 (3.9875) 0.769 (1.8408) Median (Min,Max) 0 (0, 6.00) 1.000 (0, 8.82) 0 (0, 12.72) 0 (0, 6.00) Wilcoxon0.5148^(b) Median 0.3751^(b) Fentanyl (μg)^(a) Mean (SD) 49.72 (72.396)3575.97 (12507.111) 51.61 (67.885) 35.46 (39.323) Median (Min, Max)36.00 (0, 300.0) 55.00 (0, 45198.8) 30.00 (0, 270.0) 33.00 (0, 120.0)Wilcoxon 0.5676^(b) Median 0.6249^(b) Abbreviations: CD = continuousdose; DEX = dexmedetomidine; LD = loading dose; MAX = maximum; midazolam= midazolam; Min = minimum Note: Dose Level 1—Dex LD = 0.25/CD = 0.2μg/kg/hr Dose Level 2—Dex LD = 0.50/CD = 0.4 μg/kg/hr Dose Level 3—DexLD = 1.00/CD = 0.7 μg/kg/hr Dose Level 4—Dex LD = 1.00/CD = 2.00μg/kg/hr ^(a)Descriptive statistics are computed based on total numberof subjects whether or not they used any amount of rescue medication forsedation during the treatment period while intubated, within each doselevel. ^(b)P-values from Proc NPAR1WAY for specified tests.

The time to first rescue medication for sedation and analgesia in thefull evaluable population, as presented in Table 25, demonstrated atrend reflecting longer median times to first rescue with increasingdose levels with similar time intervals for Dose Levels 2 and 3treatment groups (2.2 and 2.5 hours), while the time to first rescuemedication was shorter for the Dose Level 1 treatment group (1.0 hours)and longer for the Dose Level 4 treatment group (7.8 hours). This trendwas not statistically significant (P=0.2391 Log-Rank), as shown in Table26. A comparable trend was observed in the safety population, except theeffect was not monotonic. The time to rescue for the Dose Level 2treatment group (2.5 hours) was slightly greater than the Dose Level 3treatment group (2.4 hours).

TABLE 25 Summary of Time (Hours) to First Dose of Rescue Medication forSedation and Analgesia - Full Evaluable Population Dose Level 1 DoseLevel 2 Dose Level 3 Dose Level 4 Overall Parameter Dex Dex Dex DexP-value^(c) Median^(a) 1.0 2.2 2.5 7.8 95% CI^(b) (0.417, 3.500) (0.600,3.333) (1.367, 3,867) (1.250)^(d) N (%)Censored 4 (25.0) 2 (15.4) 1(7.1) 6 (42.9) Log-Rank 0.2391 Wilcoxon 0.2021 Abbreviations: CD =continuous dose; DEX = dexmedetomidine; LD = loading dose; MAX =maximum; midazolam = midazolam; Min = minimum Note: Dose Level 1—Dex LD= 0.25/CD = 0.2 μg/kg/hr Dose Level 2—Dex LD = 0.50/CD = 0.4 μg/kg/hrDose Level 3—Dex LD = 1.00/CD = 0.7 μg/kg/hr Dose Level 4—Dex LD =1.00/CD = 2.00 μg/kg/hr ^(a)Descriptive statistics are computed based ontotal number of subjects whether or not they used any amount of rescuemedication for sedation during the treatment period while intubated,within each dose level. ^(b)P-values from Proc NPAR1WAY for specifiedtests. ^(c)P-value from Log-Rank and Wilcoxon tests for differencebetween treatment groups (using PROC LIFETEST with strata dose level).^(d)CI lower bound only. No upper bound.

In Group I, the mean total doses were 30.9200, 100.1147, 94.0000, and663.5800 μg for the Dose Level 1, 2, 3, and 4 treatment groups,respectively, with the exception of the Dose Level 3 treatment groupthat showed a small decrease, exposure generally increased as the doselevel increased. In Group II, the mean total doses were 73.1150,236.9350, 269.2444, and 586.2825 μg for the Dose Level 1, 2, 3, and 4treatment groups. For all treatment groups in Group II, exposureincreased as the dose level increased. The total exposure todexmedetomidine for the safety population is given in Table 27 below.

TABLE 27 Total Exposure for Dexmedetomidine - Safety Population GroupI - Dose Level Group II - Dose Level 1 2 3 4 1 2 3 4 Mean Total 30.9100.1 94.0 663.6 73.1 236.9 269.2 586.3 Dose (μg)

Summary statistics for the dexmedetomidine loading doses and maintenanceinfusion doses are shown in Table 27A below.

TABLE 27A Summary Statistics of Dosing-Related Data Dose-Related 0.25μg/kg + 0.50 μg/kg + 1.00 μg/kg + 1.00 μg/kg + Variable 0.20 μg/kg/h0.40 μg/kg/h 0.70 μg/kg/h 2.00 μg/kg/h Loading dose (ng) Mean (SD)7021.333 (6098.953) 12237.143 (7955.193) 28765.333 (21368.168) 36904.286(35112.824) Median 4400.000 9800.000 23400.000 20900.000 Min, Max2800.00, 24800.00 5200.00, 35480.00 12000.00, 98000.00  12000.00,140000.00 n 15 14 15 14 Maintenance Mean (SD) 42797.333 (33346.443)108335.571 (86027.962) 170381.333 (151015.142) 473520.000 (196870.668)infusion dose (ng) Median 26520.000 104400.000 117600.000 462200.000Min, Max 12000.00, 125200.00 22760.00, 360920.00  58800.00, 595600.00153080.00, 828800.00 n 15 14 15 14 Total dose (ng) Mean (SD) 49818.667(38564.475) 120572.714 (92121.808) 199146.667 (158726.350) 510424.286(202156.184) Median 32000.000 117000.000 141600.000 474800.000 Min, Max14800.00, 150000.00 33200.00, 396400.00  70800.00, 635200.00 165880.00,892360.00 n 15 14 15 14 Loading infusion Mean (SD) 0.167 (0.000)  0.167(0.000) 0.167 (0.000) 0.167 (0.000) duration (h) Median 0.167 0.1670.167 0.167 Min, Max 0.17, 0.17  0.17, 0.17  0.17, 0.17 0.17, 0.17 n 1514 15 14 Maintenance Mean (SD) 7.919 (3.855) 11.514 (6.771) 8.792(5.371) 10.196 (4.837)  infusion Median 6.000 7.000 7.000 7.075 duration(h) Min, Max  487, 15.83 2.25, 20.82  2.50, 20.25  6.00, 17.67 n 15 1415 14 Time between Mean (SD) 10.533 (1.302)  10.214 (0.579) 10.400(1.298)  10.357 (1.336)  start of doses Median 10.000 10.000 10.00010.000 (min) Min, Max 10.00, 15.00  10.00, 12.00  10.000, 15.00  10.00,15.00 n 15 14 15 14 Time from end of Mean (SD) 0.533 (1.302)  0.214(0.579) 0.400 (1.298) 0.357 (1.336) 1^(st) to beginning of Median 0.0000.000 0.000 0.000 2^(nd) infusion (min) Min, Max 0.00, 5.00  0.00, 2.00 0.00, 5.00 0.00, 5.00 n 15 14 15 14

The mean dexmedetomidine concentration profiles (over time) for the DoseLevels 1 and 2 were similar and remained generally the same over time asillustrated in FIG. 1. For the Dose Level 3 treatment group, the meanplasma dexmedetomidine concentration showed a sharp increase at the endof the loading dose compared to other dose levels. The sharp increasewas the result an excessively high plasma dexmedetomidine concentrationat the end of the loading dose in a subject (Subject 123009) in the DoseLevel 3 treatment group. Subject 123009 had a mean area under theconcentration-time curve from time zero to the time of the lastmeasurable concentration (AUC_(0-t))=116910.2 μg/mL/hr and area underthe concentration-time curve from time zero to the time infinity(AUC_(0-∞))=117264.1 μg/mL/hr, and C_(max)=28804.30 μg/mL). Mean plasmaconcentrations of dexmedetomidine tended to increase with increasingdose levels. The highest mean plasma concentrations were observed in theDose Level 4 treatment group. The mean concentration at the end of themaintenance infusion, AUC, C_(ss), and C_(max) values increased withincreasing dose.

The mean half-life values for the Dose Level 1, 2, 3, and 4 treatmentgroups (combined across age groups) were 1.546, 1.743, 2.045, and 2.145hours, respectively. The apparent increase in half-life with increasingdose levels is due to many of the concentrations used to calculate thehalf-life for the lower dose levels being below the limit ofquantitation.

Statistically significant differences were observed between Groups I andII within each dose level for the pharmacokinetic parameters of V_(d)(p=0.0046), weight adjusted V_(d) (p=0.0040), and CL (p=0.0078), andweight adjusted CL (p=0.0094), as shown in Table 28.

TABLE 28 Summary of Statistically Significant Differences Between GroupI and Group II Subjects Within Each Dose Level for PharmacokineticParameters - Full Evaluable Population Geometric Means^(a,b) Parameter/Dose Level 1 Dose Level 2 Dose Level 3 Dose Level 4 Statistics DEX N =16 DEX N = 14 DEX N = 15 DEX N = 14 P-Value Group I V_(d) 36.91 31.7746.64 36.29 CL 16.24 12.73 16.59 11.93 Group II V_(d) 51.70 61.17 46.5872.82 CL 24.69 24.76 16.44 25.36 Differences^(c) V_(d) −0.337 −0.6550.001 −0.696 0.0046 (−1.399, 0.725) (−1.096, −0.215) (−0.626, 0.628)(−1.212, −0.181) CL −0.419 −0.665 0.009 −0.754 0.0078 (−1.669, 0.831)(−1.068, −0.262) (−0.663, 0.680) (−1.389, −0.119) Abbreviations: CD =continuous dose; CL = plasma clearance; DEX = dexmedetomidine; LD =loading dose; PK = pharmacokinetics; V_(d) = volume of distributionNote: Dose Level 1—Dex LD = 0.25/CD = 0.2 μg/kg/hr Dose Level 2—Dex LD =0.50/CD = 0.4 μg/kg/hr Dose Level 3—Dex LD = 1.00/CD = 0.7 μg/kg/hr DoseLevel 4—Dex LD = 1,00/CD = 2.00 μg/kg/hr

Statistically significant differences (p<0.05) were observed in PKparameters by dose level for AUC_(0-t), C_(max), t_(1/2), C_(ss) and λzand by age for Css (p=0.0167), C_(max) (p=0.0053), V_(d) (p=0.0089) andCL (p=0.0125), and weight adjusted V_(d) (p=0.0055) and CL (p=0.0190).

Pharmacokinetic parameters of dexmedetomidine in the full evaluablepopulation were summarized using descriptive statistics and arepresented in Table 29. Similar results were obtained in subjects thatunderwent cardiopulmonary bypass surgery.

TABLE 29 Summary of Pharmacokinetic Parameters - Full EvaluablePopulation Parameter/ Dose Level 1 Dose Level 2 Dose Level 3 Dose Level4 Statistics DEX DEX DEX DEX Primary Pharmacokinetic ParametersAUC_(0-t) 14 13 14 14 [(μg/ mL)hr] (N) Mean (SD) 2681.332 (2353.3418)6460.576 (3766.4657) 16992.540 (29927.3911) 28531.864 (17496.3985)Median 1540.417 (779.88, 9266.09) 5247.638 (1900.23, 12194.00) 5606.310(4257.50, 116910.2) 25411.857 (10027.42, 68850.45) (Min, Max) % CV 87.7758.30 176.12 61.32 AUC_(0-∞) 12 13 14 14 [(μg/ mL)hr] (N) Mean (SD)3153.518 (3343.3451) 6673.163 (3781.2183) 17300.539 (29935.7647)28970.541 (17936.8970) Median 1583.539 (923.23, 12681.98) 5521.515(2023.22, 12413.04) 6078.304 (4568.71, 117264.1) 25675.767 (10093.96,70764.26) (Min, Max) % CV 106.02 56.66 173.03 61.91 C_(max) 14 13 14 14(μg/mL)(N) Mean (SD) 480.437 (625.9946) 847.691 (633.7352) 3385.569(7384.0699) 3090.939 (1625.5241) Median 266.465 (169.58, 2558.19)581.040 (399.60, 2456.03) 966.235 (534.11, 28804.30) 2686.210 (1540.85,6810.13) (Min, Max) % CV 130.30 74.76 218.10 52.59 T_(max) 14 13 14 14(hours)(N) Mean (SD) 7.307 (5.7937) 8.805 (9.5105) 2.174 (2.7535) 6.815(5.9039) Median 6.042 (0.08, 16.17) 5.683 (0.12, 20.93) 0.367 (0.08,6.33) 5.417 (0.13, 17.60) (Min, Max) % CV 79.29 108.01 126.66 86.63t_(1/2) 12 13 14 14 (hours)(N) Mean (SD) 1.546 (0.3401) 1.743 (0.3018)2.045 (0.6582) 2.145 (0,6763) Median 1.556 (1.03, 2.28) 1.687 (1.27,2.45) 1.795 (1.24, 3.33) 2.125 (0.98, 3.33) (Min, Max) % CV 22.00 17.3132.18 31.53 λ_(z) (1/ 12 13 14 14 hour)(N) Mean (SD) 0.469 (0.1062)0.408 (0.0672) 0.369 (0.1037) 0.360 (0.1350) Median 0.446 (0.30, 0.67)0.411 (0.28, 0.54) 0.386 (0.21, 0.56) 0.326 (0.21, 0.71) (Min, Max) % CV22.64 16.46 28.13 37.56 C_(ss) 12 13 14 14 (μg/mL)(N) Mean (SD) 402.026(535.1718) 539.848 (166.7423) 1347.284 (1308.0988) 2827.144 (1169.4226)Median 197.991 (149.71, 2056.54) 513.902 (282.31, 868.84) 947.907(637.50, 5743.55) 2665.409 (1602,66, 5429.48) (Min, Max) % CV 133.1230.89 97.09 41.36 V_(d) (L)(N) 12 13 14 14 Mean (SD) 61.982 (66.0605)50.632 (26.2671) 52.328 (25.5848) 62.186 (34.7628) Median 42.960 (13.76,238.30) 40.657 (23.67, 95.26) 51.303 (17.22, 100.71) 57.802 (23.17,138.40) (Min, Max) % CV 106.58 51.88 48.89 55.90 V_(ss) (L)(N) 12 13 1414 Mean (SD) 56.808 (44.5127) −8.363 (156.5060) 32.789 (22.5478) 43.652(30.6577) Median 40.264 (4.25, 144.02) 30.633 (−522.63, 83.53) 30.400(3.38, 88.22) 33.114 (12.09, 122.08) (Min, Max) % CV 78.36 −1871.3068.77 70.23 Weight- 12 13 14 14 adjusted V_(d) (L/kg)(N) Mean (SD) 2.167(0.8564) 2.315 (0.8392) 2.441 (1.3576) 2.484 (0.9016) Median 2.429(0.28, 3.38) 2.486 (1.31, 4.04) 2.187 (0.57, 5.83) 2.152 (1.19, 4.41)(Min, Max) % CV 39.53 36.24 55.62 36.30 CL (L/hr)(N) 12 13 14 14 Mean(SD) 32.208 (40.3982) 20.268 (10.3508) 18.565 (8.6995) 22.199 (14.1623)Median 19.531 (5.37, 147.15) 16.040 (10.43, 39.50) 16.170 (3.76, 39.47)16.890 (7.42, 49.96) (Min, Max) % CV 125.43 51.07 46.86 63.80 Weight- 1213 14 14 adjusted CL (L/hr/kg)(N) Mean (SD) 1.039 (0.4826) 0.939(0.3021) 0.842 (0.3339) 0.849 (0.3010) Median 1.196 (0.11, 1.65) 0.884(0.55, 1.66) 0.881 (0.13, 1.27) 0.803 (0.35, 1.28) (Min, Max) % CV 46.4632.88 39.65 35.44 Abbreviations: λz = terminal elimination rateconstant; AUC_(0-∞) = area under the concentration-time curve from timezero to the time infinity; AUC_(0-t) = area under the concentration-timecurve from time zero to the time of the last measurable concentration;CD = continuous dose; CL = plasma clearance; C_(max) = observed peakplasma concentration; C_(ss) = steady state concentration; CV =coefficient of variation; DEX = dexmedetomidine; LD = loading dose; Max= maximum; Min = minimum; T_(max) = time of maximum concentration;t_(1/2) = terminal elimination half-life; V_(d) = volume ofdistribution; V_(ss) = volume of steady state distribution. Note: DoseLevel 1—Dex LD = 0.25/CD = 0.2 μg/kg/hr Dose Level 2—Dex LD = 0.50/CD =0.4 μg/kg/hr Dose Level 3—Dex LD = 1.00/CD = 0.7 μg/kg/hr Dose Level4—Dex LD = 1.00/CD = 2.00 μg/kg/hr

Plasma clearance over age, weight and weight-adjusted clearance over ageare presented in FIGS. 2-4, respectively. Weight-adjusted clearance for2-year-old patients was approximately 1 L/hr/kg and decreased with ageuntil values were approximately that observed in adults (0.6 L/kg/hr).

The pharmacokinetic analysis demonstrated dose proportionality and alinear relationship among the Dose Level 1, 2, 3, and 4 treatment groupsand AUC and C_(max). The predicted mean curves for AUC_(0-∞), AUC_(0-t),C_(max), and C_(ss) generated using the power fit model are presented inFIGS. 6-9, respectively. As dose increased, AUC and C_(max) increased inproportion (FIG. 1 and Table 29).

AUC_(0-∞) and AUC_(0-t) of dexmedetomidine displayed positive linearityamong the Dose Level 1, 2, 3, and 4 treatment groups. The C_(max) ofdexmedetomidine displayed positive linearity for the Dose Level 1, 2,and 3 treatment groups and showed a slight decrease in the Dose Level 4treatment group. The apparent t_(1/2) of dexmedetomidine was 1.546,1.743, 2.045, and 2.145 hours for the Dose Level 1, 2, 3, and 4treatment groups, respectively. Statistically significant differenceswere observed between Groups I and II only for the pharmacokineticparameters of V_(d) (p=0.0046), weight-adjusted V_(d) (p=0.0040), CL(p=0.0078), and weight-adjusted CL (p=0.0094). Weight-adjusted clearancedecreased with age until values were approximately that observed inadults. No noticeable increases or decreases in V_(d) or weight-adjustedV_(d) for increasing age or weight were observed.

Statistically significant differences were observed for thepharmacokinetic parameters for the main effect of dose level forAUC_(0-t), AUC_(0-∞), C_(ss), C_(max), λz, and t_(1/2) and the maineffect age for C_(ss), C_(max), V_(d), weight-adjusted V_(d), CL, andweight-adjusted CL using a two-way analysis of variance (ANOVA).However, there were no statistically significant dose level by age groupinteractions observed for any of the pharmacokinetic parameters. Asummary of key pharmacokinetic parameters for the full evaluablepopulation is given in Table 30 below.

TABLE 30 Summary of Key Pharmacokinetic Parameters for the FullEvaluable Population Dose Level 1 Dose Level 2 Dose Level 3 Dose Level 4Parameter DEX (N = 14) DEX (N = 13) DEX (N = 14) DEX (N = 14)P-value^(a) AUC_(0-t) 2681.3 (2353.34) 6460.6 (3766.47) 16992.5(29927.39) 28531.9 (17496.40) <0.0001 [(pg/mL)hr] C_(max) (pg/mL) 480.4(625.99) 847.7 (633.74) 3385.6 (7384.07) 3090.9 (1625.52) <0.0001t_(1/2) (hr) 1.5 (0.34) 1.7 (0.30) 2.0 (0.66) 2.1 (0.68) 0.0381AUC_(0-∞) 3153.5 (3343.35) 6673.2 (3781.22) 17300.5 (29935.76) 28970.5(17936.90) <0.0001 [(pg/mL)hr] C_(ss)(pg/mL) 402.0 (535.17) 539.8(166.74) 1347.3 (1308.10) 2827.1 (1169.42) <0.0001 λ_(z) (1/hr) 0.5(0.11) 0.4 (0.07) 0.4 (0.10) 0.4 (0.14) 0.0381 V_(d) (L) 62.0 (66.06)50.6 (26.27) 52.3 (25.58) 62.2 (34.76) 0.8210 Weight-adjusted 2.2 (0.86)2.3 (0.84) 2.4 (1.36) 2.5 (0.90) 0.6394 V_(d) (L/kg) CL (L/hr) 32.2(40.40) 20.3 (10.35) 18.6 (8.70) 22.2 (14.16) 0.8439 Weight-adjusted 1.0(0.48) 0.9 (0.30) 0.8 (0.33) 0.8 (0.30) 0.8769 CL (L/hr/kg)Abbreviations: λz = terminal elimination rate constant; AUC_(0-∞) = areaunder the concentration-time curve from time zero to the time infinity;AUC_(0-t) = area under the concentration-time curve from time zero tothe time of the last measurable concentration; CL = plasma clearance;C_(max) = observed peak plasma concentration; C_(ss) = steady stateconcentration; DEX = dexmedetomidine; LD = loading dose; t_(1/2) =terminal elimination half-life; Vd = volume of distribution. ^(a)Resultsof two-way analysis of variance (ANOVA) to evaluate the effect of doselevel on age group for PK parameters. Note: Dose Level 1—Dex LD =0.25/CD = 0.2 μg/kg/hr Dose Level 2—Dex LD = 0.50/CD = 0.4 μg/kg/hr DoseLevel 3—Dex LD = 1.00/CD = 0.7 μg/kg/hr Dose Level 4—Dex LD = 1.00/CD =2.00 μg/kg/hr

The pharmacodynamic parameters measured in Groups I and II were level ofsedation, number of subjects who received rescue medication (midazolamand fentanyl), amount of rescue medication required for sedation andanalgesia, vital signs (HR, SBP, DBP, MAP, RR, and SpO₂), time tosuccessful extubation, and comparison of RSS_(avg) with AUC_(0-∞) andC_(ss). The RSS scores (e.g., RSS₅ and RSS_(avg)) were generally similaracross dose levels and between Groups I and II, although the RSS₅ andRSS_(avg) scores in the Dose Level 4 treatment group of Group II wereslightly higher compared to other treatment groups in Groups I and II.For subjects that received dexmedetomidine alone, the RSS₅ and RSS_(avg)scores were higher across treatment groups in Group II compared to GroupI. For subjects that received dexmedetomidine with the co-administrationof midazolam or fentanyl, the RSS₅ and RSS_(avg) scores were generallysimilar between subjects in all treatment groups and across age groupswith the exception of subjects in the Dose Level 4 treatment group inGroup II. The RSS5 and RSS_(avg) scores in the Dose Level 4 treatmentgroup of Group II (RSS5=4.5 and RSS_(avg)=4.5) were slightly highercompared to other treatment groups (RSS5 scores range=2.5 to 3.7) inGroups I and II in the full evaluable population. Similar results wereobserved in the safety population.

As described above, one subject in the Dose Level 3 treatment group hadextremely high plasma dexmedetomidine concentration at the end of theloading infusion. The plasma concentration data from this subject skewedthe calculated AUC and C_(ss) results. FIGS. 10 and 11 show therelationship between RSS_(avg) and AUC and C_(ss), respectively. Withthis subject, who had a mean AUC value of 117264.1 μg hr/mL and C_(ss)of 5743.55 μg/mL, excluded from the analyses, there was an increase inRSS_(avg) with increasing AUC and C_(ss).

A smaller percentage of subjects in Group II received rescue midazolamfor sedation compared to Group I across all treatment groups. Incomparison to the other three dose level treatment groups, fewersubjects in the Dose Level 4 treatment group required rescue medication.There was also an increase in the time to the administration of thefirst dose of rescue medication in this treatment group in the DoseLevel 4 treatment group, because of the increased level of sedation inthis treatment group. The differences between these age groups in thenumber of subjects that received rescue midazolam were not statisticallysignificant in any age group at any dose level. The amount of rescuemedication required for sedation and analgesia during the treatmentperiod was similar across all dose levels. No statistically significantdifferences were observed in the amount of midazolam or fentanyl used asrescue medication for sedation or analgesia between treatment groups inthe safety population. In general, the majority of subjects treatedacross age groups and dose levels required co-administration ofmidazolam or fentanyl with dexmedetomidine with the exception of GroupII Dose Level 4 treatment group, in which 3 of 8 subjects receivedco-administration of midazolam or fentanyl.

In the full evaluable population, the median times to extubationincreased with dose. The time intervals for the Dose Levels 1, 2, and 3treatment groups were similar (0.6-1.7 hours), while the time toextubation Dose Level 4 treatment group was longer (6.8 hours). Theeffect was not statistically significant (p=0.3041). Similar resultswere seen for the safety population. The summary of time to successfulextubation for the full evaluable population is given in Table 31 below.

TABLE 31 Summary of Time to Successful Extubation - Full EvaluablePopulation Parameter Dose Level 1 Dose Level 2 Dose Level 3 Dose Level 4Overall P-value^(c) Median^(a) 0.6 0.8 1.7 6.8 — 95% CI^(b) (0.433,3.000) (0.533, 2.417) (0.633, 4.417) (0.667, 7.333) — N (%) Censored 3(18.8) 0   2 (14.3) 2 (14.3) — Log-Rank — — — — 0.3041 Wilcoxon — — — —0.1555 Abbreviations: CD = continuous dose; CI = confidence interval;DEX = dexmedetomidine; LD = loading dose; Note: Summary of time tosuccessful extubation was done using Kaplan-Meier Estimates, Log-Rankand Wilcoxon tests. Note: Dose Level 1—Dex LD = 0.25/CD = 0.2 μg/kg/hrDose Level 2—Dex LD = 0.50/CD = 0.4 μg/kg/hr Dose Level 3—Dex LD =1.00/CD = 0.7 μg/kg/hr Dose Level 4—Dex LD = 1.00/CD = 2.00 μg/kg/hrNote: If extubation was successful, the subject is considered to havethe event. If the subject did not complete the treatment/discontinued,the subject is censored. ^(a)Median time to successful extubation fromstart of DEX infusion in hours. ^(b)95% CI for median. ^(c)P-value fromLog-Rank and Wilcoxon tests for difference between treatment groups(using PROC LIFETEST with strata dose level).

No clinically meaningful trends in the mean change from baseline in HR,SBP, DBP, MAP, RR, or SpO₂ were observed in Group I and Group IIsubjects during infusion and post-infusion. Similarly, no clinicallymeaningful trends were seen in the mean change from baseline in HR, SBP,DBP, or MAP in subjects stratified by whether or not they underwentcardiopulmonary bypass surgery.

Treatment-related adverse events occurred primarily during the loadingdose and only in Dose Levels 3 and 4. The most frequently reported nondrug-related treatment emergent adverse effects in both age groups werepyrexia, vomiting, hypokalaemia, and hypertension. In Group I (26subjects), the treatment-related TEAEs were bradycardia (2 subjects),hypotension (1 subject), sedation (2 subjects), hypertension (1subject). In Group II (33 subjects), the treatment-related TEAEs werebradycardia (1 subject), sedation (1 subject), hypertension (5subjects), and chills (1 subject).

The majority of these adverse effects were considered not related to thestudy drug and mild or moderate in intensity. Numerical differences wereobserved in several hematology, chemistry, and urinalysis parameterswith increasing or decreasing trends among treatment groups inlymphocytes, neutrophils, platelets, ALP, AST, and bilirubin. Althoughnumerical changes occurred, no clinically meaningful trends in the meanchange from baseline in HR, SBP, DBP, MAP, RR, and SpO2 betweentreatment groups were observed among treatment groups. Respiratory ratewas not affected. Similar results were obtained in subjects stratifiedby whether or not they underwent cardiopulmonary bypass surgery.

The change from Baseline in SBP tended to increase from Dose Level 1 to4 for subjects who underwent CPB surgery. These differences were notclinically significant. No similar observation was noted in subjects whodid not undergo CPB surgery.

Except for the slightly higher SBP observed in subjects who underwentCPB surgery in the Dose Level 4 treatment group, the 4 dose levels ofdexmedetomidine studied were generally well tolerated in this study andthere were no clinically meaningful differences observed between doselevels in the safety profile of dexmedetomidine.

There were no clinically meaningful changes from baseline in theclinical laboratory test results observed across treatment groups duringinfusion and post-infusion. Hematology results that showed largenumerical changes from Baseline included lymphocytes, neutrophils, andplatelets. Chemistry results that showed large numerical changes fromBaseline included ALP, AST, and bilirubin.

The majority of ECG findings reported were normal or abnormal but notclinically significant. The majority of subjects had unremarkablephysical examination findings in all body system categories except thecardiopulmonary body system. No clinically meaningful changes in vitalsigns, laboratory test results or ECGs were observed across treatmentgroups during infusion and post-infusion. In general, dexmedetomidinewas well tolerated in intubated and mechanically ventilated pediatricpatients in this study.

No deaths were reported. One subjected experienced convulsion that wasconsidered mild and not related to study drug. Drug-relatedtreatment-emergent adverse effects (TEAEs) were reported at Dose Levels3 and 4, as shown in Table 32.

TABLE 32 Drug-Related Treatment-Emergent Events by Preferred Term -Safety Population Group I DEX Dose DEX Dose DEX Dose DEX Dose Level 1Level 2 Level 3 Level 4 (N = 8) (N = 6) (N = 6) (N = 6) Subjects with atleast 1 0 0 1 (16.7) 4 (66.7) Drug-Related TEAE, n (%) Number ofDrug-related 0 0 2 4 TEAE Bradycardia 0 0 1 (16.7) 1 (16.7) Sedation 0 00 2 (33.3) Hypertension 0 0 1 (16.7) 0 Hypotension 0 0 0 1 (16.7) GroupII DEX Dose DEX Dose DEX Dose DEX Dose Level 1 Level 2 Level 3 Level 4(N = 8) (N = 8) (N = 9) (N = 8) Subjects with at least 1 0 0 2 (22.2) 4(50.0) Drug-Related TEAE, n (%) Number of Drug-related 0 0 3 4 TEAEBradycardia 0 0 1 (11.1) 0 Chills 0 0 1 (11.1) 0 Sedation 0 0 0 1 (12.5)Hypertension 0 0 1 (11.1) 3 (37.5) Abbreviations: DEX = dexmedetomidine;TEAE = Treatment Emergent Adverse Events. Investigator adverse event(AE) terms were coded to preferred terms using Medical Dictionary forRegulatory Activities (MedDRA) dictionary version 11.0). Percentages arebased on the number of subjects in each treatment group by age group.Subjects are counted once within each system organ class or for eachpreferred term and may have had more than 1 TEAE. Related is any eventthat was assessed as either unknown relation, unlikely, possibly,probably/likely or certainly related to study medication. If a subjecthad more than one occurrence of the same TEAE, the highest relationshipto study drug was summarized. Note: Dose Level 1—Dex LD = 0.25/CD = 0.2μg/kg/hr Dose Level 2—Dex LD = 0.50/CD = 0.4 μg/kg/hr Dose Level 3—DexLD = 1.00/CD = 0.7 μg/kg/hr Dose Level 4—Dex LD = 1.00/CD = 2.00μg/kg/hr

Example 4: Effects of Dexmedetomidine in the Prenatal Cynomolgus MonkeyBrain

The study was conducted to determine the potential neuroapoptotic effectof dexmedetomidine in prenatal Cynomolgus monkey brains by administeringdexmedetomidine to pregnant monkeys. The overall objective of this studywas to demonstrate that dexmedetomidine, an anesthetic with a differentmechanism of action than that of isoflurane or ketamine, does not causeneuroapoptosis in prenatal cynomolgus monkey brains. The purpose of theimmunohistochemistry analysis of this study was to assess andcharacterize the regions of interest histopathologically, and tocharacterize and compare test article-induced apoptosis between groups.

The monkey model used is that described in Slikker et al. Tox. Sci.2007; 98(1), 145-58, which is hereby incorporated by reference in itsentirety. The fetus was removed from the pregnant female at 120±7 daysgestation after a 12 hour intravenous fusion of dexmedetomidine followedby a 6 hour post-infusion observation period. The fetal brain wascollected by cesarean section. The treatment groups are shown in Table33 below.

TABLE 33 Experimental design Groups (n = 5) Treatment Route ofadministration Dose 1 Cage control Not applicable Not applicable 2Ketamine Intramuscular + 20 mg/kg im + Intravenous infusion 20-50mg/kg/hr 3 Dexmedetomidine Intravenous injection + 3 ug/kg × Intravenousinfusion 10 min + 3 ug/kg/hr 4 Dexmedetomidine Intravenous injection +30 μg/kg × Intravenous infusion 10 min + 30 μg/kg/hr

Following treatment, animals were sacrificed, and brain tissues werefixed in 10% neutral buffered formalin via perfusion. A vibratomemicrotome was used to generate serial unstained brain sections at 50- to70-μm thicknesses, yielding approximately 800 sections per brain. Fixedbrain tissue was processed from 20 animals. For each animal,approximately 25 intervaled sections per brain were stained with thefollowing stains: hematoxylin and eosin (H&E), silver stain, terminaldeoxynucleotidyl transferase dUTP nick end labeling (TUNEL), andactivated Caspase 3 (AC3). The sections were evaluated by an AmericanCollege of Veterinary Pathologists (ACVP) board-certified pathologist,including the use of image analysis to assess and compare the incidenceand distribution of apoptotic cells in the TUNEL- and AC3-stainedsections.

Fixed tissues were gross trimmed, processed, oriented and embedded inparaffin, and sectioned at approximately 35- to 40-μm thicknesses. Eachbrain was carefully oriented and gross trimmed into each block to assurecorrelative symmetry between animals. Six consecutive blocks wereprepared for each brain and spanned the entire frontal cortex.Approximately 100 unstained sections were microtomed for each block fora total of about 600 sections per animal. For each block, section level1, 25, 50 and 100 were selected for staining. Assessments were conductedto assure that the section levels selected and examine correlated wellbetween animals. Assessments were also conducted to confirm that theketamine-induced lesions were confined to the 1 and 2 layers of thefrontal cortex and that the lesion was distributed consistently in thisregion in all animals as reported by Slikker. Approximately 25 serialsections from each brain were stained by one of the followingtechniques. H&E stain was used to define general histology andmorphology. Silver staining was used to visualize neurodegeneration.TUNEL is a method for detecting DNA fragmentation by labeling theterminal end of nucleic acids. AC3, detected by IHC antibody staining,is a marker for apoptotic cells. Following staining, tissues wereevaluated by light microscopy by a board-certified veterinarypathologist. All procedures were consistent with CBI SOPs; details aremaintained in the study records.

The modified silver method was employed on brain sections. See Xuemin Yeet al. 2001, Brain Research Protocols 8, 104-112, which is herebyincorporated by reference in its entirety. Briefly, the sections werede-waxed in xylene and rehydrated in alcohol. The following steps wereemployed: dehydrate with 50, 75, and 97% 1-propanol for at least 5minutes each; esterified in sulfuric acid/1-propanol at 56° C. for 16hours; rehydrate with 50 and 25% 1-propanol followed by two changes ofdistilled water, 5 minutes each; wash with 1% acetic acid for exactly 10minutes; place in the developing solution until the sections turn brownin color (ca. 6-8 minutes); terminate development by washing with 1%acetic acid (30 minutes); and dehydrate, clear and cover slip.

For activated caspase 3 staining, tissues were deparaffinized, hydrated,and subjected to heated citrate buffer antigen retrieval. Tissues werestained on a DAKO Autostainer. Tissues were reacted with peroxidase andtwo protein blocks. Following rinsing in buffer, tissues were thenincubated at room temperature for 60 minutes with 1:275 dilution of AC-3(Abcam) followed by incubation for 30 minutes with Envision goatanti-rabbit secondary antibody (Envision). The immunoreaction wasvisualized with DAB and counterstaining with hematoxylin. Both positive(human tonsil) and negative tissues (human uterus), plus tissues stainedwith irrelevant antibody and with saline were included.

For TUNEL staining, tissues were deparaffinized, hydrated, and subjectedto heated citrate buffer antigen retrieval. Tissues were stained eitheron a DAKO Autostainer or were hand stained using the Trevigen TACS2TdT-DAB In Situ Apoptosis Detection Kit. Both positive (human tonsil)and negative tissues (human uterus), plus tissues stained withirrelevant antibody and with saline were included.

Extensive areas of the frontal cortex and multiple levels through thefrontal cortex were examined with special emphasis on the lamina. Theremainder of the brain tissue on the slides was also examined for anyother lesions. Representative photomicrographs were taken.H&E-silver-stained, TUNEL and AC3 sections were qualitatively examinedby the Study Pathologist, a veterinary pathologist certified by theAmerican College of Veterinary Pathologists (ACVP). The incidence andseverity of the lesions (presence of apoptosis and cell injury) werescored using the accepted industry scoring system: 0=normal, 1=minimal,2=mild, 3=moderate; and 4=severe.

Severity scoring of the treatment-related findings is presented in Table34. There were abundant neuroapoptotic lesions of the cortex present inthe ketamine-treated group, while there were minimal changes seen in thedexmedetomidine-treated groups, particularly in thelow(therapeutic)-dose group.

TABLE 34 Summary of severity scoring of neuroapoptotic lesions FetalBrains Activated Group Treatment Dose Examined HE Silver caspase 3 TUNEL1 Cage control Untreated 5 0.0 ± 0.0 0.6 ± 0.6 0.8 ± 0.6 0.0 ± 0.0 2Ketamine 20 mg/kg 5 1.9 ± 1.2 2.0 ± 0.8 3.5 ± 0.7 2.9 ± 1.1 im + 20-50mg/kg/hr 3 Dexmedetomidine 3 ug/kg × 5 0.1 ± 0.3 1.0 ± 1.1 1.4 ± 0.6 0.1± 0.2 10 min + 3 ug/kg/hr 4 Dexmedetomidine 30 μg/kg + 5 0.0 ± 0.1 0.4 ±0.6 1.8 ± 0.9 0.8 ± 0.9 30 μg/kg/hr

Severity scoring of the treatment-related findings is presented in Table34. Representative photomicrographs of TUNEL staining of frontalcortexes are shown in FIG. 12. Representative photomicrographs of AC3staining of frontal cortexes are shown in FIGS. 13 and 14.Representative photomicrographs of silver staining of frontal cortexesare shown in FIG. 15.

In Group 1, untreated brains, examination of HE, Silver, TUNEL and AC3stained sections from the frontal cortex demonstrated no or rare,sporadically damaged and apoptotic cells in the layers of frontalcortex. There was some low intensity positive nuclear AC3 stainingparticularly in the white matter, which is indicative of normal fetaldevelopment. There were also a few TUNEL positive cells in other areasof the brain, but there were no differences between control and treatedbrains.

In Group 2, the ketamine-treated group, examination of HE, Silver, TUNELand AC3 sections from the frontal cortex demonstrated a moderate tolarge number of damaged and apoptotic cells that was dramaticallyincreased in comparison to untreated and dexmedetomidine-treated brains.AC3 marks neurons that are undergoing apoptotic degeneration afterexposure to apoptogenic drugs including isoflurane. AC3 stained cellsare also the same cells that are stained by silver stains that markcells that are dead or dying. AC3 also reveals if cells are in an earlyor advanced state of degeneration and what type of cell is undergoingdegeneration (Bambrink, 2010). In early states, there is abundant AC3protein in the cell body and processes, therefore the degenerate cellcan be visualized microscopically. Following cell death, the cell bodybecomes condensed and rounded up.

Both of these morphologies were abundantly visible in ketamine-treatedbrains but were minimally visible in the dexmedetomidine-treated brains.The lesions seen in this study were characterized by a moderatemultifocal amount of necrolytic debris, degenerate axons and cell bodiesand apoptotic nuclei in the layers of the I-VI lamina of the cortex withthe most intense staining in layer I and II. The cell types affectedincluded cells with the morphology and arborization patterns ofγ-aminobutyric acid-ergic inhibitory interneurons (layer II) and smallpyramidal neurons (likely glutamateric, thought to project to the visualneurons in the contralateral hemisphere) (Bambrink, 2010). Affectedlarge multipolar neurons (commonly in layers V and VI), large and smallpyramidal neurons (layers IV and V) and interneurons in layer II werealso evident.

These observations are very similar to those described by Bambrink, 2010with isoflurane-treated rhesus monkeys. There were also sporadic AC-3positive cells scattered in the deeper white matter in all groups,including control.

In Group 3, the low dose dexmedetomidine group, examination of HE,Silver, TUNEL and AC3 stained sections from the frontal cortexdemonstrated a low number of damaged and apoptotic cells in comparisonto ketamine-treated brains. The lesions were characterized by a mildmultifocal amount of necrolytic debris, degenerate axons and cell bodiesand apoptotic nuclei of the 1st and 2nd layers of cortex. The same celltypes were involved as was seen with ketamine, only the numbers weremarkedly reduced in comparison to ketamine. Their incidence and severitywas also less then that seen with the higher dose of dexmedetomidine.

In Group 4, the high dose dexmedetomidine group, examination of HE,Silver, TUNEL and AC3 stained sections from the frontal cortexdemonstrated a low number of damaged and apoptotic cells that wasincreased in comparison to ketamine-treated brains. The lesions werecharacterized by a mild multifocal amount of necrolytic debris,degenerate axons and cell bodies and apoptotic nuclei of the 1st and 2ndlayers of cortex. The same cell types were involved as was seen withketamine, only the numbers were markedly reduced in comparison toketamine.

The results from this study indicate that treatment with 20 mg/kgIM+20-50 mg/kg/hr ketamine was associated with marked neuroapoptosis andcellular damage with necrosis primarily in layers I and II of thecortex. This was a diffuse and uniform multifocal to diffuse lesionextending through the frontal cortex including layers I-VI, butprimarily in layers 1 and 2. There were no significant neuroapoptoticlesions present in the untreated group. In animals receivingdexmedetomidine there was no to minimal neuroapoptosis present followingeither 3 ug/kg×10 min+3 ug/kg/hr or 30 ug/kg×30 min+3 ug/kg/hr. Lesionswere less severe in the low-dose animals, indicative of a dose responseand the lesions were clearly much less severe than the ketamine treatedanimals. These findings suggest that dexmedetomidine is not associatedwith significant neuroapoptosis. In particular, these findings suggestthat dexmedetomidine is not associated with significant neuroapoptosisat the low dose.

Example 5: Pharmacokinetics of Dexmedetomidine in Pediatric PatientsAged 1 Month to 24 Months

The present study characterizes the pharmacokinetic and pharmacodynamicprofile of dexmedetomidine administered as an intravenous (IV) loadingdose followed by a continuous IV infusion in pediatric subjects.

A 36-patient, open-label, single center, escalating dose study ofdexmedetomidine was conducted on pediatric subjects who werepostoperative from cardiac surgery. The study investigated thepharmacokinetics and pharmacodynamics of dexmedetomidine. The subjectswere 1 month to 24 months old with tracheal intubation or mechanicalventilation in the immediate postoperative period, and planned trachealextubation within 24 hours after surgery. The subjects received one ofthe doses given in Table 35 below.

The primary objectives of this study were as follows:

-   -   To define the pharmacokinetics of increasing doses of        dexmedetomidine administered as an intravenous bolus followed by        a continuous IV infusion (CIVI) in infants who were        postoperative from cardiac surgery.    -   To describe the pharmacodynamic effects of dexmedetomidine in        infants (age: 1 month to 2 years) who were post-operative        surgical patients during the 24-hour period prior to, and        during, extubation.

The secondary objectives were as follows:

-   -   To obtain correlation data on the relationship between level of        sedation and dexmedetomidine plasma drug concentration in        infants post-operative from cardiac surgery and    -   To evaluate safety in the 1 month to 2 year old patient        population.

This was a single center, phase I dose escalation pharmacokinetic studyof a single bolus dose of dexmedetomidine followed by a continuousinfusion for up to 24 hours, in infants who were immediatelypost-operative from cardiac surgery and required tracheal intubationwith mechanical ventilation in the post-operative period. Thisdose-response study of dexmedetomidine in infants consisted of twophases: a screening/enrollment phase, and a dose escalation phase.

Patients whose parents or legal guardians provided informed consent werescreened within 7 days prior to enrollment. The screening/enrollmentphase was performed first. Infants (1 month to 2 years of age) who werepre-operative from surgery were screened. Infants were eligible for thestudy if they were post-operative from cardiac surgery and requiredmechanical ventilation in the post-operative period with trachealextubation expected within the first 24 post-operative hours. Enrollmentcriteria had to have been met within 7 days prior to enrollment. Thedose escalation phase followed the screening/enrollment phase. Allpatients received 4 mg/kg orally of pentobarbital, an intra-operative IVdose of 20 g/kg of fentanyl, an IV dose of 0.2 mg/kg of pancuronium oninduction and another 0.2 mg/kg on institution of bypass. Three bolusand infusion dose combinations of dexmedetomidine were administered asfollows: cohorts of 12 patients each received either low-dosedexmedetomidine (0.35 μg/kg IV bolus administered over 10 minutes, 0.25μg/kg/hour continuous IV infusion), moderate-dose dexmedetomidine (0.7μg/kg IV bolus administered over 10 minutes, 0.5 μg/kg/hour continuousIV infusion) or high-dose dexmedetomidine (1 μg/kg IV bolus over 10minutes, 0.75 μg/kg/hour continuous IV infusion). Dexmedetomidineinfusion was continued during the extubation process and trachealextubation occurred when patients had met the respiratory criteria.Inter-patient dose escalation is shown in Table 35.

TABLE 35 Inter-Patient Escalation Continuous IV Dose Loading DoseInfusion Rate Level (μg/kg) (μg/kg/hour) 1 0.35 0.25 2 0.7 0.5 3 1 0.75

Twelve patients were studied at each dose level. If more than 2 patientsat a dose level experienced a dose-limiting toxicity (DLT) that waspossibly, probably, or definitely related to study drug, the maximumtolerated dose (MTD) for the drug would have been exceeded and noadditional patients would be studied at that dose level. If the MTD wasexceeded at the first dose level, then the subsequent cohort of patientswould be treated at a loading dose of 0.25 μg/kg and an infusion of 0.14μg/kg/hour. If the MTD had been exceeded at the second or third doselevels, enrollment to the protocol would have been stopped.

The decision to escalate the dose was based on the review of safety andpharmacokinetic data for all patients in the previous cohort. If themedian clearance was less than 70% of that reported in the adultpopulation (35 L/hour), then accrual to the study was stopped.

This dose escalation study included dose cohorts of 1) 0.35 μg/kg bolus,0.25 g/kg/hour infusion; 2) 0.7 μg/kg bolus, 0.5 μg/kg/hour infusion; 3)or 1 g/kg bolus, 0.75 g/kg/hour infusion. This study providedpharmacokinetic data that would allow for improved dosingrecommendations in a critically ill population of patients (infants whowere post-operative from cardiac surgery and required mechanicalventilation in the post-operative period). This population of patientsincluded, but was not limited to, infants diagnosed with Teratology ofFallot, atrio-ventricular canal defects, ventricular septal defects,coarctation of the aorta, bi-directional glen, hemi-fontan, and fontancompletions. The Bispectral Index Scale (BIS) was used to measuresedation, and explore the utility of a non-invasive measurement ofsedation in infants who were postoperative from cardiac surgery. Also,this study was designed to obtain preliminary data on the relationshipbetween the level of sedation and dexmedetomidine plasma drugconcentration in infants postoperative from cardiac surgery. Safety wasalso evaluated in this study.

A patient was eligible for study participation if he or she met thefollowing criteria: was ≥1 month and ≤24 months of age; waspost-operative from cardiac surgery with tracheal intubation/mechanicalventilation in the immediate post-operative period; had planned trachealextubation within 24 hours post-operatively; adequate renal function(defined as serum creatinine ≤0.6 mg/dL at age 1 month to 12 months orserum creatinine ≤1.0 mg/dL at age >12 months to 24 months); adequateliver function (defined as total bilirubin ≤1.5 mg/dL and serum glutamicpyruvic transaminase (SGPT)≤165 U/L for 1 month to 12 months and ≤90 U/Lfor >12 months to 24 months); had isolated heart surgery; and allparents or legal guardians of the patient signed a written informedconsent.

A patient was not eligible for study participation if he or she met anyof the following criteria: received another investigational drug withinthe past 30 days or received continuous infusions of muscle relaxants inthe post-operative setting; had a positive blood culture without asubsequent negative culture or other evidence of ongoing seriousinfection; in the opinion of the investigator, would not be able tocomply with the safety monitoring requirements of the study; showedsigns or symptoms of elevated intracranial pressure (including, but notlimited to, Cushing's triad (hypertension, bradycardia, and bradypnea),lethargy, bulging fontanelle, and seizures; had post-operativehypotension based on age (1 month to 2 months: systolic ≤45 mm Hg,diastolic ≤25 mm Hg, or mean arterial blood pressure ≤35 mm Hg; >2months to 6 months: systolic ≤55 mm Hg, diastolic ≤35 mm Hg, or meanarterial blood pressure ≤45 mm Hg; and >6 months to 24 months: systolic≤65 mm Hg, diastolic ≤45 mm Hg, or mean arterial blood pressure ≤55 mmHg); or had pre-existing bradycardia based on age (1 month to 2 months:heart rate ≤90 bpm; 2 months to 12 months: heart rate ≤80 bpm; >12months to 24 months: heart rate ≤70 bpm); had a heart block; weighed <5kg; or who, in the opinion of the investigator, was not an appropriatecandidate for an investigational drug study.

Patients were discontinued from the study if any of the followingoccurred: there was a DLT, including bradycardia, hypotension,oversedation, or serious adverse effect; the patient's parent/guardianrefused further protocol therapy; non-compliance that, in the opinion ofthe investigator, did not allow for ongoing participation in the study;and the investigator judged that withdrawal was in the best interest ofthe patient.

Patients who were off protocol therapy were followed until they met theoff-study criteria which was defined as 30 days after the last dose ofthe investigational agent, death, lost to follow up, or withdrawal ofconsent for any further data submission. Follow-up data were requiredunless consent was withdrawn.

Eligible patients, who met all the inclusion criteria and none of theexclusion criteria, received 4 mg/kg orally of pentobarbitalpremedication, an intra-operative dose of 20 g/kg of fentanyl, 0.2 mg/kgof pancuronium on induction and another 0.2 mg/kg on institution ofbypass as intra-operative anesthetic. This was followed byadministration of study drug where dexmedetomidine (0.35 μg/kg, 0.7μg/kg, or 1 g/kg) was administered as an IV loading dose over 10 minutesfollowed by a continuous maintenance IV infusion of 0.25 g/kg/hour, 0.5μg/kg/hour, or 0.75 μg/kg/hour. Patients received one of threeloading/maintenance regimens of dexmedetomidine as follows: cohorts of12 patients received low-dose dexmedetomidine (0.35 g/kg bolus, 0.25μg/kg/hour infusion), moderate-dose (0.7 μg/kg bolus, 0.5 μg/kg/hourinfusion) or high-dose dexmedetomidine (1 μg/kg bolus, 0.75 μg/kg/hourinfusion). Dexmedetomidine infusion was continued during the extubationprocess and tracheal extubation occurred when patients had met therespiratory criteria.

Study drug consisted of the test drug (investigational product),Precedex® (dexmedetomidine HCl injection), 118 μg of dexmedetomidine and9 μg of sodium chloride in water, IV. The study drug was supplied as aclear, colorless, isotonic solution with a pH of 4.5. The solution waspreservative free and contained no additives or chemical stabilizers. Itwas freely soluble in water with a pKa of 7. Dexmedetomidine wasobtained by commercial supply for this study and was stored in thePharmacy at a controlled room temperature of 15° C. to 30° C. (59° F. to86° F.). Freezing was avoided.

Patients who met the selection criteria were enrolled in the study.Thirty-eight patients were enrolled in this study. Thirty-six patientscompleted the study drug infusion: 12 patients in each of the low,moderate and high dose cohorts. Randomization was not conducted in thisstudy; this was a dose escalation study of a single bolus ofdexmedetomidine followed by a continuous IV infusion for up to 24 hoursin infants immediately post-operatively.

The study drug, dexmedetomidine, was administered as a bolus dose over10 minutes followed by a continuous IV infusion to patients who returnedfrom the operating room tracheally intubated, with planned trachealextubation within 24 hours. Twelve patients were studied at each doselevel. If more than 2 patients at a dose level experienced a DLT thatwas possibly, probably, or definitely attributable to the study drug,the MTD for the drug was considered to be exceeded and no additionalpatients were studied at that dose level. If the MTD was exceeded at thefirst dose level, then the subsequent cohort of patients were to betreated at a loading dose of 0.25 μg/kg and an infusion of 0.14μg/kg/hr. If the MTD had been exceeded at the second or third doselevels, enrollment to the protocol would have been stopped. The doselevels were studied consecutively with pharmacokinetic analysisfollowing the completion of each dose level. If the median clearance wasless than 70% of that reported in the adult population (35 L/hr),accrual to the study was stopped. This was an unblinded study.

Patients were not allowed to receive continuous infusions of musclerelaxants in the postoperative setting. Additional sedation or analgesiain the form of fentanyl (0.25 to 1 g/kg/dose), morphine (10 to 100μg/kg/dose), or midazolam (10 to 100 μg/kg/dose) was allowed for thosepatients who were identified by the clinical team as being “undersedated”. Any additional sedation medications, the dose, route ofadministration, and date and time of administration were recorded. Anymedications taken during the study, other than the study drug, wererecorded.

It is statistically reliable and clinically relevant to use powerassessment and confidence intervals to detect dose proportionality, inwhich dose increases with an expected proportional increase in both AUCand C_(max). The University of Michigan Sedation Score (UMSS) is avalidated pediatric sedation scale and is used as a pharmacodynamicmeasurement for the Example 5 study. Other pharmacokinetic, PD, andsafety measurements in this study are widely used and are generallyrecognized as reliable, accurate, and relevant for the study. Thepharmacokinetic variables for assessment included: observed peak plasmaconcentration (C_(max)), time of observed peak plasma concentration(T_(max)), area under the plasma concentration-time curve from time zeroto the last quantifiable time point (AUC_(0-t)), area under the plasmaconcentration-time curve from time zero to infinity (AUC_(0-inf)),terminal elimination rate constant (λz), terminal half-life (t_(1/2)),end of infusion concentration (steady state, C_(ss)), plasma clearance(Cl), weight adjusted clearance (Cl_(w)), volume of distribution(V_(d)), and weight adjusted volume of distribution (V_(dw)). Theprimary PD variables assessed the level of sedation using BIS and theUniversity of Michigan Sedation Scale Safety variables included exposureto study drug, adverse events (adverse effects), hepatotoxicity, DLT,laboratory results, vital signs, use of concomitant medication, and12-lead electrocardiogram.

For the drug concentration measurements, approximately 14 mL of blood(14 samples per patient) were collected from each patient. Blood samples(1 mL) were collected in heparinized tubes for pharmacokineticevaluation of plasma dexmedetomidine. For the low dose treatment group,blood samples were collected at time zero for the bolus dose, at the endof the bolus dose, at 0.5 hours after start of infusion, at the end ofthe maintenance infusion, and at 0.25, 0.5, 1, 2, 4, 8, 12, and 24 hoursafter the end of the maintenance infusion. For the remaining cohorts,blood samples were collected prior to the bolus dose, in close proximityto 0.5, 1, 2, and 4 to 6 hours after the start of the infusion, at 15-30minutes prior to end of infusion (EOI), and at 0.25, 0.5, 1, 2, 4, 8,12, and 15 to 18 hours after the EOI. Samples were collected from adifferent site than that of the infusion site. Samples were notcollected from the 2nd lumen of the multi-lumen catheter through whichthe drug was administered. The exact time that the sample was collectedalong with the exact time that the drug was administered were recorded.Plasma was separated and stored at −80° C. until assayed. The lowerlimit of quantification in plasma is ≤4.24 μg/mL for dexmedetomidine.Each heparinized tube was labeled with the patient's study number, thestudy identification number, and the date and time that the sample wascollected. Data were recorded on the Pharmacokinetic Study Form, whichaccompanied the sample.

The primary pharmacokinetic evaluation was to define thepharmacokinetics of increasing doses of dexmedetomidine administered asan IV bolus followed by a continuous IV infusion in infants who werepostoperative from cardiac surgery. Data from all fully evaluablepatients (those receiving at least 2 hours of dexmedetomidine infusion)were included in the analysis.

The pharmacodynamic assessments monitored continuously every hour until24 hours after the discontinuation of the infusion included heart rate,blood pressure, mean arterial blood pressure, cardiac rhythm, oxygensaturation, and respiratory rate. The Bispectral Index Scale (BIS,Aspect Medical Systems, Natick, Mass.) and the University of MichiganSedation Scale (UMSS) were used to assess the level of sedation.

The Bispectral Index Scale (BIS) integrates various electroencephalogram(EEG) descriptors into a single variable. The BIS readout is adimensionless number scaled from 100 to 0, with 100 representing anawake EEG and zero representing complete electrical silence (corticalsuppression). BIS and hypnotic drug dose have been shown to correspondto a statistically significant, linear, monotonic fashion duringclinical trials, with BIS decreasing as the hypnotic dose is increased.The BIS monitor was applied to the patient's forehead prior to the bolusdose, and remained until the EOI. A member of the clinical teamperiodically did a sensor check to be sure signal quality and propersensor application/adhesion were maintained. BIS values, with theexception of the Signal Quality Index (SQI) were blinded.Pre-stimulation BIS values were recorded for sedation assessments (orduring non-stimulated times). The maximal BIS reading during stimulationwas also recorded. The “resting” BIS values or those at non-stimulatedtimes, along with the change in BIS with stimulation, were valuable inassessing not only the sedation drug effect, but also the analgesicproperties of the drug, and thus provided better data to assess the PDof the drug. The investigators were blinded to the BIS readout untilafter the study was completed. The maximum BIS readout and thecorresponding SQI were recorded for each hour that the patient was onstudy. The BIS sensor was removed from the patient's head after theinfusion had been discontinued, and the patient had been declared awakeby the clinical care team.

The UMSS is a simple, valid and reliable tool that facilitates rapid andfrequent assessment and documentation of depth of sedation in children.The UMSS is a simple observational tool that assesses the level ofalertness on a 5-point scale ranging from 1 (wide awake) to 5(unarousable with deep stimulation). The UMSS score was assessed by theclinical nurse caring for the patient, and recorded every hour until theBIS sensor was removed.

Adverse events were reported in a routine manner at scheduled timesduring the trial. Certain adverse effects were reported in an expeditedmanner to allow for optimal monitoring of patient safety and care.Adverse events were reviewed at bi-weekly meetings by the principalinvestigator (PI), co-PI, and study coordinator. Events were classifiedas either adverse effects or serious adverse effects.

An adverse effect was defined as any untoward medical occurrence thatpresented itself during treatment or administration with apharmaceutical product and which may or may not have a causalrelationship with the treatment. A treatment-emergent adverse event(treatment-emergent adverse effect) was defined as any adverse effectwith onset or worsening reported by a patient from the time that thefirst dose of study drug was administered until 24 hours had elapsedfollowing discontinuation of study drug administration. An adverseeffect that occurred during the treatment period was defined as anyadverse effect with onset or worsening reported by a patient from thedate/time of the start of study drug administration until the data/timeof study drug discontinuation. An adverse effect that occurred poststudy drug was defined as any adverse effect with onset or worseningreported by the patient at a date/time which was later than thedate/time of study drug discontinuation within the specific period.Adverse events were also classified by severity (mild, moderate, orsevere). A serious adverse effect was defined as any untoward medicaloccurrence that at any dose resulted in death, was life threatening,required inpatient hospitalization or prolongation of existinghospitalization, created persistent or significantdisability/incapacity, or a congenital anomaly/birth defect. MedWatchreports were completed for each event. Events were classified by thetreating clinician and study coordinator. Events were classified asunlikely, possibly, or probably related to the study drug and eitherpreviously described (expected), or undescribed (unexpected). The PI wasnotified by pager or telephone of any serious adverse effects. Alldrug-related and previously undescribed toxicities were reviewed within24 hours by the PI. Serious adverse effects that were expected becauseof the surgical procedure did not require expedited review and werereviewed bi-weekly. Previously undescribed toxicities and all seriousadverse effects were reported to the RB in writing by the investigatorwithin 72 hours of the event. A letter summarized any adverse reactionsor events that occurred, and the event outcome was described. If morethan one unexpected or previously described serious adverse effectattributable to study drug was observed, accrual to the protocol wassuspended. An ad hoc committee comprising the PI, subspecialty leadinvestigator, and at least 2 subspecialists not participating in thetrial were convened by the PI within 24 hours of the second event. Anassessment of the risks to patients were made, and a recommendation tocontinue with the study or close the trial were made to the RB forreview. If a decision was made to continue with the trial, themodifications to the protocol, the updated assessment of risks andbenefits, and a modified informed consent were to be submitted to theIRB.

A dose limiting toxicity (DLT) was defined as any of the events that arepossibly, probably, or definitely attributable to dexmedetomidine andfall under the following:

-   -   bradycardia defined by age: heart rate ≤80 bpm (1 month to 2        months); heart rate ≤70 bpm (>2 months to 12 months); heart rate        ≤60 bpm (>12 months to 24 months)    -   hypotension defined by age:    -   systolic ≤40 mm Hg, diastolic ≤20 mm Hg, or mean arterial blood        pressure (MAP)≤30 mm Hg (1 month to 2 months)    -   systolic ≤50 mm Hg, diastolic ≤30 mm Hg, or MAP ≤40 mm Hg (>2        months to 6 months)    -   systolic ≤60 mm Hg, diastolic ≤40 mm Hg, or MAP K 50 mm Hg (>12        months to 24 months)    -   bradypnea: respiratory rate ≤14 bpm in extubated patients    -   oversedation deemed clinically relevant by the clinical care        providers or requiring intervention. Clinical signs included        difficulty arousing with moderate stimulation, bradypnea        (respiratory rate ≤14), bradycardia, and hypotension and    -   serious adverse event.

Laboratory data for the clinical laboratory tests was collected asstandard of care were also reviewed during the study and includedarterial blood gas, lactate, basic metabolic panel, magnesium,phosphorus, coagulation panel, liver function panel, and complete bloodcount. Approximately 14 mL of blood was collected from each patient forthe clinical laboratory tests during the study.

Additional safety assessments were carried out including physicalexamination, 12-lead electrocardiogram, hepatotoxicity, andsedation/analgesia supplemental medication titration.

The statistical analyses were performed using SAS, version 9.1.Pharmacokinetic parameters were determined by non-compartmental analysisusing WinNonlin Pro Version 5.1. All statistical tests were two-sided,and p-values ≤0.05 were considered statistically significant (afterrounding to 4 decimal places), unless specified otherwise. Descriptivestatistics (number of patients [N], mean, median, standard deviation(SD), minimum, and maximum) were used to summarize continuous variables.Coefficient of variation (CV) was calculated for continuouspharmacokinetic variables. For T_(max) (a discrete variable), N, median,minimum and maximum were displayed. The mean and median were displayedto one decimal place more than the raw value. For categorical variables,N and percent were shown. All percentages were reported to one decimalplace. Patient listings of all collected and recorded data as well asderived variables were presented. Changes noted between analyses definedin the protocol and those defined in the SAP included:

There were two discrepancies between the study and the protocol. Oneregarded the definition of a DLT. The study defines DLT to includebradycardia and hypotension defined by age, and clinically relevantoversedation, and serious adverse effects as DLTs. The protocol includedonly bradycardia defined by age, hypotension defined by age, andbradypnea defined by respiratory rate.

Another discrepancy was in regards to the collection of ECG data. Theprotocol stated that ECGs were obtained pre- and post-treatment andcompared for evidence of new ischemia. ECG charts and QT intervals werenot available and there was no plan to analyze the ECG data.

The protocol referenced collection of plasma samples for pharmacogenomictesting; however, no samples were collected for pharmacogenomic testingor analysis.

Four patient populations were defined in this study.

Enrolled Population: All patients who signed inform consent were in theEnrolled Population.

Intent-to-Treat (ITT) Population: Patients who were treated and wereprotocol compliant were included in the ITT Population.

Safety Population: All patients who received study drug were included inthe Safety Population. This population was used in all safety analyses.

Pharmacokinetic Analysis Population: All patients who received at least2 hours of dexmedetomidine infusion were included in the PharmacokineticAnalysis Population.

Plasma samples were assayed for dexmedetomidine concentrations. Thefollowing parameters were calculated for each patient: AUC_(0-t),AUC_(0-inf), C_(max), T_(max), Cl, Cl_(w), V_(d), weight adjusted volumeof distribution (V_(dw)), λz, t_(1/2), and C_(ss). Area under the plasmaconcentration-time curve (AUC) and C_(max) were the primarypharmacokinetic parameters.

Model-independent methods were used by Hospira to determine thepharmacokinetic parameters described above using Non-CompartmentalAnalysis of WinNonlin version 5.1 (Pharsight, Mountain View Calif.,USA). Summary statistics for these parameters were tabulated. Geometricmeans and coefficients of variation were presented for AUC and C_(max).

An assessment of dose proportionality was made for AUC and C_(max) amongthe dose levels administered within an age group and overall. The PowerAnalysis approach and data visualization techniques were used for thisassessment.

Dose proportionality was evaluated statistically using the Power Model.The Power Model has the form: parameter=a(dose)b×random error, where aand b are the coefficient and exponent, respectively of the equation.The power model was analyzed using linear regression after logtransformation using the following equation:ln(parameter)=ln(a)+b×ln(dose)+random error. Dose proportionality wasconcluded if the 95% confidence interval (CI) for b included 1 or, b=0(HO) was not rejected when applied to dose-normalized parameters.

Data visualization techniques included the plotting of weight adjustedclearance over age, AUC, and C_(max) against administered dose todetermine if trends were present in the data that would indicate theneed for further assessment.

An exploratory assessment of a potential pharmacokinetic/PD relationshipwas undertaken. The relationship of PD parameters such as sedation levelor need for rescue sedation medication and pharmacokinetic parametersAUC or C_(max) were explored.

The pharmacodynamic analysis was summarized by dose level for ITT andPharmacokinetic Populations. The PD assessments contained sedationlevels and vital signs that were monitored continuously every hour until24 hours after the discontinuation of the infusion. Parameters includedheart rate, blood pressure, MAP, cardiac rhythm, oxygen saturation andrespiratory rate. Descriptive statistics (arithmetic mean, SD, median,minimum and maximum) were calculated for quantitative PD data as well asfor the changes from Baseline by dose level. The BIS and the UMSS wereused to assess the level of sedation.

The UMSS score was summarized by count and percentage of patients foreach sedation level by dose level. The number and percentage of patientsusing fentanyl, morphine, or midazolam during study drug administrationwas summarized by dose level and treatment differences were assessed byFisher's Exact Test. The total amount of fentanyl, morphine, andmidazolam was summarized descriptively for each dose level, and by timeperiod after the start of infusion in each dose level. The time framewas to be analyzed for total amount of sedation medication after startof infusion at 4 hours, 4 to 8 hours, 8 to 12 hours, and 0 to 24 hours.Exploratory analysis was performed for the relationship between exposureof pharmacokinetic parameters (such as AUC, C_(max), or C_(ss)) andusage of sedation medication (such as total dose).

Descriptive statistics were used to summarize vital signs measurementsfor heart rate, blood pressure, temperature, mean arterial bloodpressure (MAP), respiratory rate, and saturation of peripheral oxygen(SpO₂) in a dose-dependent manner with time compared with Baseline.Treatment differences in the mean change from Baseline on each timepointwere assessed by one-way analysis of variance (ANOVA) with treatmentfactor in the model.

All safety data were listed by patients. Safety data included exposureof study drug, adverse effects, cardiac ischemia, liver function tests,DLT assessments, clinical laboratory evaluations, physical exams, andthe use of concomitant medications. Descriptive statistics (arithmeticmean, SD, median, minimum and maximum) were calculated for quantitativesafety data as well as for the difference from Baseline, whenappropriate.

The exposure to study medication was quantified according to the bolusdose and maintenance dose of study drug administered. Loading dose (orbolus dose) was summarized using the parameters of total dose andduration of dose. Maintenance dose was summarized using the total dose,and total duration of dose (in hours). Total dose equaled loadingdose+CIVI rate×duration of dose. Duration of dose and total hours ofdose were both calculated using time of last administration minus timeof first administration, excluding interruptions. The patient's weightwas carried forward to use in dose calculation.

Adverse events were coded using the most updated version of the MedicalDictionary for Regulatory Activities (MedDRA Version 11.0) available andsummarized by dose level for the number of patients reporting theadverse effect and the number of adverse effects reported. A by-patientadverse effect data listing included verbatim term, coded term,treatment group, severity, and relationship to treatment provided.Serious adverse events associated with death and adverse effects leadingto discontinuation of study drug were also summarized and listed. Atreatment-emergent adverse effect was defined as any adverse effect withonset or worsening reported by a patient from the time that the firstdose of study drug was administered until 24 hours had elapsed followingdiscontinuation of the study drug. For summaries by severity, if apatient had multiple events occurring in the same system organ class(SOC) or same preferred term, then the event with the highest severitywas summarized. Any adverse effect with a missing severity wassummarized as severe. Similar methodology was applied to relationship tostudy drug.

Laboratory test results for change from Baseline were tabulateddescriptively by treatment. All laboratory values outside the normalrange were flagged in the data listings. Patients were evaluated by bodysystem and were categorized as normal or abnormal. Since ECG charts andQT intervals were not available, ECG data were not analyzed. A summaryof hepatotoxicity was presented by number and percentage of patients bydose level in each scheduled visit.

The sample size was based on the determination of the pharmacokineticprofile of dexmedetomidine. Based on an estimated inter-patientvariability of 50% for steady state concentration, a sample size of 36evaluable patients was to be sufficient to detect a difference (alpha0.05, power 80%) for AUC and C_(ss) between the three dosing groups.Twelve evaluable patients were to be enrolled into each dose group.Based on clinical intensive care unit (CICU) patient census, it wasestimated that 15 months would be required to complete enrollment.

Patient disposition is summarized in Table 36.

TABLE 36 Disposition of Patients - Enrolled Patients Low Dose^(a)Moderate Dose^(b) High Dose^(c) Total Patients (%) N = 12 N = 12 N = 14N = 38 Patients who completed treatment 12 (100.0) 12 (100.0) 12 (85.7)36 (94.7) Patients who prematurely 1 (8.3)  0  2 (14.3)^(d) 3 (7.9)discontinued study Patients in Safety Population 12 (100.0) 12 (100.0) 14 (100.0)  38 (100.0) Patients in Intent-to-Treat 12 (100.0) 12(100.0) 12 (85.7) 36 (94.7) Population Patients in Pharmacokinetic 12(100.0) 12 (100.0) 12 (85.7) 36 (94.7) Population ^(a)Low-dosedexmedetomidine (0.35 μg/kg bolus, 0.25 μg/kg/hour infusion).^(b)Moderate-dose dexmedetomidine (0.7 μg/kg bolus, 0.5 μg/kg/hourinfusion). ^(c)High-dose dexmedetomidine (1.0 μg/kg bolus, 0.75μg/kg/hour infusion). ^(d)Two patients in the high dexmedetomidine dosegroup discontinued the study and were not included in the ITTPopulation.

Thirty-eight patients were enrolled into the study and assigned into oneof 3 treatment groups: low-dose dexmedetomidine (0.35 μg/kg bolus, 0.25μg/kg/hour infusion), moderate-dose dexmedetomidine (0.7 μg/kg bolus,0.5 μg/kg/hour infusion), or high-dose dexmedetomidine (1.0 μg/kg bolus,0.75 μg/kg/hour infusion). Of the 38 enrolled patients, 3 (7.9%)discontinued the study prematurely. One patient in the low-dosedexmedetomidine treatment group completed study drug infusion andsubsequently discontinued the study. Two patients in the high-dosedexmedetomidine treatment group discontinued the study prematurely;these patients were not included in the Pharmacokinetic Population. 36of the 38 enrolled patients (94.7%) completed treatment.

All 38 patients enrolled into the study received at least 1 dose ofstudy medication and were included in the Safety Population. Thirty-sixpatients received at least 2 hours of dexmedetomidine infusion and hadsufficient concentration data to calculate the primary pharmacokineticparameters; these patients were included in the PharmacokineticPopulation. Thirty-six patients in the ITT Population completedtreatment.

Patients who prematurely discontinued treatment were recorded. Protocoldeviations were also recorded. Demographics of the patient populationwere collected as well as medical and birth history. Prior andconcomitant medications were also recorded.

Summary statistics for the dexmedetomidine loading doses and maintenanceinfusion doses are shown in Table 37.

TABLE 37 Summary Statistics of Dosing-Related Data 0.35 μg/kg + 0.70μg/kg + 1.00 μg/kg + Dose-Related Variable 0.25 μg/kg/h 0.50 μg/kg/h0.75 μg/kg/h Loading dose (ng) Mean (SD) 2782.000 (701.169)  5144.417(1169.842) 7468.333 (1759.374) Median 2620.000 4907.000 6850.000 Min,Max 1876.00, 4165.00 3787.00, 7070.0  5100.00, 11200.00 n 12 12 12Maintenance infusion Mean (SD) 17699.500 (14649.792) 34790.417(18282.909) 57580.000 (29129.275) dose (ng) Median 13638.000 31060.50045864.000 Min, Max  7375.00, 61707.00 10443.00, 68425,00  2669.00,117300.00 n 12 12 12 Total dose (ng) Mean (SD) 20481.500 (14922.818)39934.833 (18364.830) 65048.333 (28941.225) Median 16589.500 35950.00053799.000 Min, Max  9853.00, 65347.00 15427.00, 73255.00 35196.00,124200.00 n 12 12 12 Loading infusion Mean (SD) 0.182 (0.021) 0.168(0.021) 0.183 (0.038) duration (h) Median 0.167 0.167 0.183 Min, Max0.17, 0.22 0.12, 0.20 0.12, 0.27  n 12 12 12 Maintenance infusion Mean(SD) 8.901 (6.055) 9.853 (6.055) 10.961 (6.635)  duration (h) Median6.610 8.619 8.708 Min, Max  4.17, 23.75  2.94, 23.82 4.18, 22.65 n 12 1212 Time between start of Mean (SD) 14.500 (2.646)  11.917 (2.610) 12.833 (1.899)  doses (min) Median 14.500 11.500 13.000 Min, Max 11.00,20.00  7.00, 17.00 10.00, 16.00  n 12 12 12 Time from end of 1^(st) Mean(SD) 3.583 (2.429) 1.833 (2.167) 1.833 (1.403) to beginning of 2^(nd)Median 3.00 1.500 2.000 infusion (min) Min, Max 1.00, 8.00 0.00, 7.000.00, 4.00  n 12 12 12

Two patients were excluded from the pharmacokinetic analysis. Bothpatients were in the high dexmedetomidine dose group. Thirty-sixpatients had sufficient concentration data to calculate thepharmacokinetic parameters and were included in the pharmacokineticanalysis set. Patients who were treated and protocol compliant wereincluded in the ITT Population. The pharmacokinetic population and ITTincluded the same patients; therefore, analysis for baselinecharacteristics was identical for the ITT and the pharmacokineticprofiles. Safety profile was analyzed for the Safety Population;thirty-eight patients received at least 1 dose of study medication andwere included in the Safety Population.

The pharmacokinetic profile demonstrated linearity and doseproportionality among 0.25, 0.50 and 0.75 μg/kg/hour dose levels; asdose increased, AUC and C_(mx) increased in proportion. The mean doseswere given as 20.5, 40.4, and 65.1 μg to 0.25, 0.50 and 0.75 μg/kg/hourdose levels, respectively), and as shown, exposure increasedaccordingly. AUC_(0-inf), AUC_(0-t) and C_(max) of dexmedetomidinedisplayed positive linearity among 0.25, 0.50 and 0.75 μg/kg/hour doselevels. The apparent t_(1/2) of dexmedetomidine was 2.33 hrs, 2.12 hrs,and 3.05 hrs for low, moderate, and high dose levels, respectively. Thegeometric mean slope among the three dose levels and the 95% confidenceintervals were 1.263 (0.820, 1.706) for AUC_(0-inf), and 0.898 (0.652,1.143) for C_(max). A similar positive linear trend was shown among thethree age groups 1 to <6 months, 6 to <12 months and 12 to 24 months.

The statistical analysis for assessing dose proportionality for thethree doses of dexmedetomidine is presented in Table 38. Doseproportionality can be concluded for AUC_(0-t), AUC_(0-inf), and C_(max)given that the 95% CI for slope included one for these parameters.

TABLE 38 Dose proportionality analysis of dexmedetomidinepharmacokinetic parameters - PK population Geometric MeansDexmedetomidine Dexmedetomidine Dexmedetomidine Low Dose^(a) ModerateDose^(b) High Dose^(c) Slope^(d) Parameter (units) N = 12 N = 12 N = 12(95% CIs) All PK Population n 12 12 12 AUC_(0-t) [hr*(ng/mL)] 1804.574163.01 7453.03 1.282 (0.835, 1.729) AUC_(0-inf) [hr*(ng/mL)] 1851.134195.77 7492.29 1.263 (0.820, 1.706) C_(max) (ng/mL) 277.59 460.66760.76 0.898 (0.652, 1.143) Age 1 to <6 months n 5 4 3 AUC_(0-t)[hr*(ng/mL)] 1630.18 4171.58 7477.55 1.380 (0.631, 2.129) AUC_(0-inf)[hr*(ng/mL)] 1668.59 4209.96 7511.57 1.362 (0.621, 2.103) C_(max)(ng/mL) 260.44 444.34 847.52 1.010 (0.455, 1.566) Age 6 to <12 months n4 6 7 AUC_(0-t) [hr*(ng/mL)] 1542.76 4647.87 8392.11 1.541 (0.828,2.255) AUC_(0-inf) [hr*(ng/mL)] 1601.44 4675.95 8435.14 1.512 (0.804,2.221) C_(max) (ng/mL) 286.81 500.04 762.71 0.891 (0.489, 1.292) Age 12to 24 months n 3 2 2 AUC_(0-t) [hr*(ng/mL)] 2634.53 2979.07 4895.660.501 (−1.098, 2.100) AUC_(0-inf) [hr*(ng/mL)] 2669.84 3010.96 4929.130.495 (−1.092, 2.083) C_(max) (ng/mL) 295.55 387.09 641.22 0.654 (0.130,1.177) ^(a)Low dose dexmedetomidine: 0.35 μg/kg bolus, 0.25 μg/kg/hourinfusion. ^(b)Moderate dose dexmedetomidine: 0.7 μg/kg bolus, 0.5μg/kg/hour infusion. ^(c)High dose dexmedetomidine: 1.0 μg/kg bolus,0.75 μg/kg/hour infusion. ^(d)Estimate slopes were computed from linearregression of log (PK parameters) versus log (dose) over dose range. CI= confidence interval

The predicted mean curve for AUC_(0-inf), AUC_(0-t), and C_(max)generated using the power fit model are presented in FIGS. 34A-C.

A linear plot illustrating the mean dexmedetomidine concentrations overtime is shown in FIG. 35. The mean dexmedetomidine concentrationprofiles (overtime) for the three treatment groups were similar, asillustrated in FIG. 35. Mean plasma concentrations of dexmedetomidinetended to increase with increased doses of dexmedetomidine. The highestmean plasma concentrations were observed in the high-dosedexmedetomidine treatment group. AUC and C_(max) values increased withincreasing dose. Half-life values were independent of dose of level. Themean half-life values for the low, moderate and high dose combinationswere 2.33, 2.12 and 3.05 hours, respectively. Pharmacokinetic parametersof dexmedetomidine were summarized using descriptive statistics and arepresented in Table 39.

TABLE 39 Summary of Pharmacokinetic Parameters - ITT PopulationParameter/ Low Dose^(a) Moderate Dose^(b) High Dose^(c) Statistics N =12 N = 12 N = 12 Primary Pharmacokinetic Parameters AUC_(0-t) (hr*ng/mL)Mean (SD) 2472.6 (2651.38) 4761.3 (2855.34) 8644.5 (5998.26) Median(Min, Max) 1656.3 (721.9, 10420.7) 3443.5 (2364.2, 10891.8) 6910(4400.6, 25990.7) % CV 107.2   60.0  69.4  AUC_(0-inf) (hr*ng/mL) Mean(SD) 2511.9 (2651.99) 4793.9 (2864.88) 8686.5 (6016.70) Median (Min,Max) 1671.9 (735.0, 10458.3) 3469.1 (2389.8, 10961.0) 6948.0 (4441.0,26078.4) % CV 105.6   59.8  69.3  C_(max) (hr/mL) Mean (SD) 300.1(116.75) 479.6 (172.99) 786.4 (233.96) Median (Min, Max) 296.5 (113,473) 440.0 (339, 1010) 683.5 (602, 1340) % CV 39   36   30   SecondaryPharmacokinetic Parameters T_(max) (hour)^(d) Median (Min, Max) 2.39(0.17, 18.98) 6.98 (1.20, 23.83) 6.13 (0.68, 22.55) % CV 130.48  73.9093.98 t_(1/2) (hour) Mean (SD) 2.33 (1.305) 2.12 (0.788) 3.05 (1.947)Median (Min, Max) 1.87 (1.14, 5.79) 2.02 (1.00, 3.89) 2.40 (1.65, 8.35)% CV 55.93 37.18 63.77 λz (1/hour) Mean (SD) 0.37 (0.151) 0.37 (0.141)0.28 (0.108) Median (Min, Max) 0.37 (0.12, 0.61) 0.34 (0.18, 0.69) 0.29(0.08, 0.42) % CV 41.34 38.17 38.19 Cl (L/hour) Mean (SD) 10.24 (3.753)9.27 (4.001) 8.49 (3.145) Median (Min, Max) 9.74 (4.30, 17.12) 8.05(4.44, 19.17) 7.84 (4.70, 15.17) % CV 36.66 43.17 37.02 Cl_(w)(L/hour/kg) Mean (SD) 1.36 (0.637) 1.24 (0.362) 1.13 (0.278) Median(Min, Max) 1.24 (0.60, 2.93) 1.24 (0.53, 2.05) 1.15 (0.69, 1.55) % CV46.90 29.27 24.62 V_(d) (L) Mean (SD) 30.54 (11.015) 27.20 (11.798)36.02 (24.467) Median (Min, Max) 29.09 (16.83, 54.09) 27.34 (11.97,48.33) 27.53 (16.21, 95.34) % CV 36.06 43.38 67.93 V_(dw) (L/kg) Mean(SD) 3.97 (1.432) 3.71 (1.693) 5.32 (4.865) Median (Min, Max) 3.53(2.01, 5.93) 3.36 (1.74, 7.75) 3.34 (2.70, 18.69) % CV 36.05 45.60 91.53^(a)Low-dose dexmedetomidine: (0.35 μg/kg bolus, 0.25 μg/kg/hourinfusion). ^(b)Moderate-dose dexmedetomidine: (0.7 μg/kg bolus, 0.5μg/kg/hour infusion). ^(c)High-dose dexmedetomidine: (1.0 μg/kg bolus,0.75 μg/kg/hour infusion). ^(d)T_(max) is presented as median only(minimum, maximum). CV = coefficient of variation, ITT =Intent-to-Treat, max = maximum, min = minimum, N, n = number ofpatients, SD = standard deviation

Clearance and weight-adjusted clearance over age are presented in FIG.36. No noticeable increase or decrease in clearance or weight-adjustedclearance for increasing age was observed. No additional regressionanalysis was performed between age and pharmacokinetic parameters.

A summary of the level of sedation, measured with the UMSS, at each timepoint during the treatment period for the enrolled population ispresented in Table 40. Patients had deep sedation (UMSS 3-4) frompre-dose to 2 hours after infusion, and maintained a moderate level ofsedation (UMSS 1-3) after 4 hours infusion through the end of infusionfor all dose levels. There was a correlated relationship between plasmaconcentration and UMSS for low dose 30 minutes after start of infusion,moderate dose 8 hours after end of infusion, and high dose 30-15 minutesprior to end of infusion and 60 minutes after end of infusion. With theUMSS, fewer patients were categorized as “unarousable” at 1 hourpost-infusion as compared with Pre-bolus/Baseline, for all threedexmedetomidine dose groups. After 1 hour of post-infusion ofdexmedetomidine, the level of sedation had decreased for all dosegroups. Patients became less sedated from the time of infusion to 6hours post-infusion. This was apparent with all 3 doses ofdexmedetomidine; the incidence of patients who were “unarousable” atPre-bolus/Baseline was 91.7%, 91.7%, and 83.3% for the low, moderate,and high-dose dexmedetomidine groups, respectively. At six hourspost-infusion, the incidence of patients who were “moderatelysedated/somnolent” was 58.3%, 41.7%, and 50.0% for each of thedexmedetomidine dose groups.

TABLE 40 Summary of Level of Sedation (UMSS) at Selected Time PointsDuring Treatment Period - ITT Population Number (%) of Patients TimePoint Low Dose^(a) Moderate Dose^(b) High Dose^(c) Characteristic N = 12N = 12 N = 12 p-values^(d) Pre-bolus/Baseline 0.5788 Awake and alert 0 00 Minimally sedated/Sleepy 1 (8.3) 0 0 Moderately sedated/Somnolent 0 00 Deeply sedated/Deep sleep 0 1 (8.3) 1 (8.3) Unarousable 11 (91.7) 11(91.7) 10 (83.3) Post-bolus/Pre-infusion 0.4288 Awake and alert 0 0 0Minimally sedated/Sleepy 1 (8.3) 0 0 Moderately sedated/Somnolent 0 1(8.3) 0 Deeply sedated/Deep sleep 1 (8.3) 2 (16.7) 0 Unarousable 10(83.3) 9 (75.0) 11 (91.7) Post Infusion Hour 1 0.4880 Awake and alert 00 0 Minimally sedated/Sleepy 1 (8.3) 0 0 Moderately sedated/Somnolent 1(8.3) 0 2 (16.7) Deeply sedated/Deep sleep 1 (8.3) 3 (25.0) 1 (8.3)Unarousable 9 (75.0) 9 (75.0) 8 (66.7) Post Infusion Hour 3 0.1834 Awakeand alert 0 0 0 Minimally sedated/Sleepy 2 (16.7) 2 (16.7) 1 (8.3)Moderately sedated/Somnolent 3 (25.0) 2 (16.7) 4 (33.3) Deeplysedated/Deep sleep 7 (58.3) 3 (25.0) 2 (16.7) Unarousable 0 5 (41.7) 4(33.3) Post Infusion Hour 6 0.8306 Awake and alert 0 1 (8.3) 1 (8.3)Minimally sedated/Sleepy 2 (16.7) 3 (25.0) 0 Moderatelysedated/Somnolent 7 (58.3) 5 (41.7) 6 (50.0) Deeply sedated/Deep sleep 1(8.3) 2 (16.7) 2 (16.7) Unarousable 1 (8.3) 1 (8.3) 1 (8.3) PostInfusion Hour 10 0.5512 Awake and alert 3 (25.0) 1 (8.3) 3 (25.0)Minimally sedated/Sleepy 2 (16.7) 4 (33.3) 2 (16.7) Moderatelysedated/Somnolent 1 (8.3) 4 (33.3) 1 (8.3) Deeply sedated/Deep sleep 2(16.7) 1 (8.3) 3 (25.0) Unarousable 0 1 (8.3) 0 Post Infusion Hour 140.5683 Awake and alert 2 (16.7) 2 (16.7) 4 (33.3) Minimallysedated/Sleepy 0 3 (25.0) 2 (16.7) Moderately sedated/Somnolent 4 (33.3)3 (25.0) 2 (16.7) Deeply sedated/Deep sleep 2 (16.7) 1 (8.3) 1 (8.3)Unarousable 0 0 0 Post Infusion Hour 18 0.3840 Awake and alert 0 1 (8.3)2 (16.7) Minimally sedated/Sleepy 2 (16.7) 3 (25.0) 0 Moderatelysedated/Somnolent 2 (16.7) 1 (8.3) 2 (16.7) Deeply sedated/Deep sleep 1(8.3) 0 0 Unarousable 0 1 (8.3) 0 Post Infusion Hour 22 0.4821 Awake andalert 1 (8.3) 1 (8.3) 0 Minimally sedated/Sleepy 0 0 0 Moderatelysedated/Somnolent 2 (16.7) 0 1 (8.3) Deeply sedated/Deep sleep 0 0 0Unarousable 0 1 (8.3) 0 Post Infusion Hour 26 — Awake and alert 0 0 0Minimally sedated/Sleepy 1 (8.3) 0 0 Moderately sedated/Somnolent 0 0 0Deeply sedated/Deep sleep 0 0 0 Unarousable 0 0 0 ^(a)Low-dosedexmedetomidine: (0.35 μg/kg bolus, 0.25 μg/kg/hour infusion).^(b)Moderate-dose dexmedetomidine: (0.7 μg/kg bolus, 0.5 μg/kg/hourinfusion). ^(c)High-dose dexmedetomidine: (1.0 μg/kg bolus, 0.75μg/kg/hour infusion). ^(d)P-values are from Cochran-Mantel-Haenszeltest. Note: Patient 33 UMSS scores were not applicable due to continuousinfusion of neuromuscular blockade. ITT = Intent-to-Treat, — = notapplicable, N = number of patients, UMSS = University of MichiganSedation Scale

A summary of the level of sedation (BIS scores) at each time pointduring the treatment period for the ITT Population was reviewed.Patients became less sedated from the time of infusion to 6 hourspost-infusion. This was more apparent with the low and moderate doses ofdexmedetomidine; the pre-infusion mean changes from Baseline maximum BISvalues were −1.0+9.72 and −5.8±13.22 for patients in the low andmoderate dose groups, respectively. Six hours post-infusion, the meanchanges from Baseline maximum BIS values were 12.7±28.52 and 14.2+12.21for patients in the low and moderate dose groups, respectively. Patientswho received the highest dose of dexmedetomidine also becameincreasingly awake with time; however, the mean changes from Baseline toup to 6 hours post-infusion were less than observed with the lowerdoses; the preinfusion mean change from the Baseline maximum BIS scorewas −8.2±13.43, and at 6 hours post-infusion it was 2.3±14.86. The SQIat each time point during the treatment period for the ITT Populationwas summarized. The SQI values were similar among the threedexmedetomidine dose groups at post-bolus dose/pre-infusion and remainedconsistently stable through 16 hours post infusion; there was morevariability after 16 hours post-infusion of dexmedetomidine.

An analysis of the correlation between the UMSS score anddexmedetomidine plasma concentration is presented in Table 41. ThePearson correlation was used to test zero correction of dexmedetomidineof plasma and UMSS scores, significant correlation was observed at thefollowing timepoints: 30 minutes after start of infusion of lowdose-dexmedetomidine (p=0.0266), 8 hours after the EOI of moderate dosedexmedetomidine (p=0.0423), and 30 to 15 minutes prior to the EOI(p=0.0255) and 60 minutes after the EOI (0.0502) of high-dosedexmedetomidine. With the exception of these time points,dexmedetomidine plasma concentrations did not correlate with UMSSsedation scores.

TABLE 41 Analysis of Correlation between the University of MichiganSedation Scale and Dexmedetomidine Plasma Concentration - ITT PopulationLow Dose^(a) Moderate Dose^(b) High Dose^(c) Timepoint/ N-12 N = 12 N =12 Statistics Dex Plasma UMSS p-value Dex Plasma UMSS p-value Dex PlasmaUMSS p-value Pre-dose n 12  12  12  12  11  11  Mean (SD) 0 3.8 (0.87) 03.9 (0.29) 0 3.9 (0.30) Median 0 4.0 (1, 4) 0 4.0 (3, 4) 0 4.0 (3, 4)(Min, Max) End of bolus n 12  12  0 0 0 0 Mean (SD) 269.7 (127.08) 3.7(0.89) 0.1517 N/A N/A — N/A N/A — Median 208.0 (106, 473) 4.0 (1, 4) N/AN/A N/A N/A (Min, Max) 30 min after start of infusion n 12  12  11  11 11  11  Mean (SD) 120.4 (31.76) 3.5 (1.00) 0.0266 250.5 (76.56) 3.5(0.69) 0.1935 390.9 (185.66) 3.8 (0.60) 0.4164 Median 125.5 (39, 155)4.0 (1, 4) 238.0 (161, 413) 4.0 (2, 4) 339.0 (146, 765) 4.0 (2, 4) (Min,Max) 60 min after start of infusion n 0 0 8 8 8 8 Mean (SD) N/A N/A —336.3 (186.45) 3.8 (0.46) 0.8044 424.4 (147.62) 3.4 (0.92) 0.9112 MedianN/A N/A 317.0 (115, 711) 4.0 (3, 4) 463.0 (138, 578) 4.0 (2, 4) (Min,Max) 2 hours after start of infusion n 0 0 11  11  11  11  Mean (SD) N/AN/A — 326.1 (127.04) 3.4 (0.81) 0.4939 560.6 (119.26) 3.2 (0.87) 0.5981Median N/A N/A 300 (159, 620) 4.0 (2, 4) 586.0 (281, 702) 3.0 (2, 4)(Min, Max) 4 to 6 hours after start of infusion n 0 0 11  11  10  10 Mean (SD) N/A N/A — 413.4 (222.55) 1.6 (1.03) 0.2884 592.9 (82.56) 2.4(0.84) 0.9560 Median N/A N/A 367.0 (112, 1010) 2.0 (0, 3) 613 (393, 689)2.0 (1, 4) (Min, Max) 6 hours after start of infusion n 7 7 0 0 0 0 Mean(SD) 230.0 (111.54) 2.3 (1.25) 0.1466 N/A N/A — N/A N/A — Median 187.0(113, 428) 2.0 (0, 4) N/A N/A N/A N/A (Min, Max) 12 hours after start ofinfusion n 2 2 0 0 0 0 Mean (SD) 299.0 (165.46) 2.0 (0.00) — N/A N/A —N/A N/A — Median 299.0 (182, 416) 2.0 (2, 2) N/A N/A N/A N/A (Min, Max)30-15 min prior to end of infusion n 0 0 11  11  9 9 Mean (SD) N/A N/A —423.6 (164.14) 1.6 (1.03) 0.5137 805.3 (281.08) 2.3 (0.50) 0.0255 MedianN/A N/A 394.0 (307, 890) 2.0 (0, 4) 686.0 (504, 1340) 2.0 (2, 3) (Min,Max) End of infusion n 12  12  0 0 0 0 Mean (SD) 220.5 (98.04) 1.5(1.09) 0.3485 N/A N/A — N/A N/A — Median 205.5 (77, 420) 2.0 (0, 3) N/AN/A N/A N/A (Min, Max) 15 min after end of infusion n 1 1 9 9 7 7 Mean(SD) 272.0 (N/A) 3.0 (N/A) — 423.3 (194.88) 1.7 (1.12) 0.3181 758.0(282.80) 2.6 (0.98) 0.3601 Median 272.0 (272, 272) 3.0 (3, 3) 383.0(254, 925) 1.0 (0, 3) 680.0 (493, 1280) 3.0 (1, 4) (Min, Max) 30 minutesafter end of infusion n 6 6 2 2 1 1 Mean (SD) 192.7 (93.68) 2.3 (1.03)0.8999 318.5 (30.41) 2.5 (0.71) — 447.0 (N/A) 2.0 (N/A) — Median 171.0(84, 347) 2.0 (1, 4) 318.5 (297, 340) 2.5 (2, 3) 447.0 (447, 447) 2.0(2, 2) (Min, Max) 60 min after end of infusion n 6 6 10  10  9 9 Mean(SD) 99.2 (68.05) 0.8 (0.75) 0.1082 310.9 (107.54) 1.7 (1.16) 0.2190504.4 (271.32) 1.6 (1.24) 0.0502 Median 85.5 (37, 216) 1.0 (0, 2) 285.0(189, 582) 1.5 (0, 4) 431.0 (115, 1080) 2.0 (0, 3) (Min, Max) 2 hoursafter end of infusion n 11  11  10  10  10  10  Mean (SD) 84.3 (59.49)1.8 (0.75) 0.8720 188.4 (67.88) 1.1 (0.88) 0.8269 351.6 (179.77) 1.3(1.6) 0.3666 Median 60.0 (31, 207) 2.0 (1, 3) 174.5 (88, 332) 1.0 (0, 2)268.5 (213, 772) 1.0 (0, 3) (Min, Max) 4 hours after end of infusion n 77 9 9 7 7 Mean (SD) 50.7 (36.09) 1.1 (0.90) 0.5451 93.8 (61.29) 0.8(1.30) 0.6763 185.3 (131.80) 1.3 (1.11) 0.1680 Median 45.0 (8, 96) 1.0(0, 2) 72.0 (28, 232) 0.0 (0, 4) 116.0 (45, 411) 1.0 (0, 3) (Min, Max) 8hours after end of infusion n 6 6 4 4 7 7 Mean (SD) 13.2 (15.04) 1.2(0.98) 0.5885 12.4 (12.45) 1.0 (0.82) 0.0423 51.2 (51.88) 0.4 (0.79)0.4667 Median 10.0 (0, 39) 1.5 (0, 2) 10.3 (0, 29) 1.0 (0, 2) 19.5 (10,143) 0.0 (0, 2) (Min, Max) 12 Hours after end of infusion n 2 2 2 2 2 2Mean (SD) 10.0 (14.14) 1.0 (1.41) — 4.2 (5.99) 1.0 (0.00) — 36.0 (26.87)1.5 (0.71) — Median 10.0 (0, 20) 1.0 (0, 2) 4.2 (0, 8) 5.0 (1, 1) 36.0(17, 55) 1.5 (1, 2) (Min, Max) 15 to 18 hours after end of infusion n 00 1 1 0 0 Mean (SD) N/A N/A — 0 (N/A) 0 (N/A) — N/A N/A — Median N/A N/A0.0 (0, 0) 0.0 (0, 0) N/A N/A (Min, Max) Note: Correlation p-values(Pearson product moment) assessed within treatment groups. ^(a)Low-dosedexmedetomidine (0.35 μg/kg bolus, 0.25 μg/kg/hour infusion).^(b)Moderate-dose dexmedetomidine (0.7 μg/kg bolus, 0.5 μg/kg/hourinfusion). ^(c)High-dose dexmedetomidine (1.0 μg/kg bolus, 0.75μg/kg/hour infusion). DEX = dexmedetomidine, ITT = Intent-to-Treat, max= maximum, min = minimum, N, n = number of patients, SD = standarddeviation, UMSS = University of Michigan sedation scale

An analysis of the correlation between UMSS scores and dexmedetomidineplasma AUC_(0-t) was conducted. The data presentation was not clinicallymeaningful.

An analysis of the correlation between the UMSS scores and Cl_(w) ofdexmedetomidine from plasma was conducted. The strongest correlation wasobserved for the low dose; significant correlations were observed atpre-infusion (p=0.0015), 1 hour post-infusion (p=0.0191), and 12 hourspost-infusion (p=0.0385). A significant correlation was also observedfor the high dose of dexmedetomidine at the time infusion wasdiscontinued (p=0.0295). An analysis of the correlation between the UMSSscores and Cl of dexmedetomidine was conducted. Significant correlationbetween UMSS scores and clearance of dexmedetomidine was observed forlow-dose dexmedetomidine at pre-infusion and 12 hours post-infusion(p=0.0371 and p=0.0470, respectively).

Only patients with sufficient pharmacokinetic data to calculate theprimary pharmacokinetic parameters were included in the pharmacokineticanalysis population. In general, missing data were not imputed.

Pharmacokinetic sample collection times and the respective observedvalues for dexmedetomidine were reviewed by patient for patients thatreceived the low dose-dexmedetomidine (0.25 μg/kg/hour), for patientsthat received the moderate-dose dexmedetomidine (0.5 μg/kg/hour), andfor patients that received the high-dose dexmedetomidine (0.75μg/kg/hour). Pharmacokinetic parameters reviewed as natural logtransformed values for dexmedetomidine. Pharmacokinetic parametersdisplayed as observed values for dexmedetomidine were also reviewed.

An analysis of the correlation between the UMSS score anddexmedetomidine plasma concentration is presented in Table 41. There wasno data presenting relationship to response. A significant correlationfor UMSS score and dexmedetomidine plasma concentration was observed atthe following timepoints: 30 minutes after start of infusion of low-dosedexmedetomidine (p=0.0266), 30 to 15 minutes prior to the end ofinfusion of high-dose dexmedetomidine (p=0.0255), and 8 hours after theend of infusion of moderate-dose dexmedetomidine (p=0.0423).

The pharmacokinetic profile demonstrated linearity and doseproportionality among 0.25, 0.50 and 0.75 μg/kg/hour dose levels; asdose increased, AUC and C_(max) increased in proportion. The mean doseswere given as 20.5, 40.4, and 65.1 μg to 0.25, 0.50 and 0.75 μg/kg/hourdose levels, respectively; as shown dose increased accordingly.AUC_(0-inf) and C_(max) of dexmedetomidine were dose-proportional at the0.25 to 0.75 μg/kg/hour dose level. The apparent t_(1/2) ofdexmedetomidine was 2.33 hrs, 2.12 hrs, and 3.05 hrs for the low,moderate, and high dose levels, respectively. The geometric mean slopeamong the three dose levels and 95% confidence intervals were 1.263(0.820, 1.706) for AUC_(0-inf), and 0.898 (0.652, 1.143) for C_(max). Adose-dependent increase in mean plasma concentration, AUC_(0-t), andAUC_(0-inf) was observed between the three dexmedetomidine dose groups.Dose proportionality was concluded for AUC_(0-t), AUC_(0-inf), andC_(max) for dexmedetomidine in this study. No notable differences inweight-adjusted clearance versus age were observed for any dose groups.

Patients had deep sedation (UMSS 3-4) from pre-dose to 2 hours afterinfusion, and maintained a moderate level of sedation (UMSS 1-3) after 4hours infusion through the end of infusion for all dose levels. Therewas a correlated relationship between plasma concentration and UMSS forlow dose 30 minutes after start of infusion, moderate dose 8 hours afterend of infusion, and high dose 30-15 minutes prior to end of infusionand 60 minutes after end of infusion.

Thirty-eight patients received at least one dose of dexmedetomidine andwere included in the safety analysis set. Two patients (assigned to thehigh-dose dexmedetomidine treatment group) did not complete the studytreatment; these patients were not included in the ITT orpharmacokinetic analysis. Twelve patients within each treatment group(36 patients total) completed study drug infusion. Exposure to studydrug is summarized in Table 42. The mean doses given to the 36 ITTpatients were 20.5, 40.4, and 65.1 μg for the 0.25, 0.50 and 0.75μg/kg/hour dose levels, respectively as shown dose increasedaccordingly. The mean duration of dose infused was approximately 9.1,10.0, and 11.2 hours for low, moderate, and high dose levels,respectively.

TABLE 42 Summary of Exposure to Dexmedetomidine (Total Dose) - ITTPopulation Low Dose^(a) Moderate Dose^(b) High Dose^(c) N = 12 N = 12 N= 12 Total dose (μg)^(d) Mean (SD) 20.5 (14.92) 40.4 (18.32) 65.1(28.91) Median (Min, Max) 16.6 (10, 65) 39.0 (15, 73) 53.9 (35, 124)Duration of Dose (min)^(e) Mean (SD) 544.8 (362.89) 601.3 (363.96) 669.0(396.82) Median (Min, Max) 407.5 (260, 1434) 526.5 (187, 1441) 533.0(264, 1369) ^(a)Low-dose dexmedetomidine: (0.35 μg/kg bolus, 0.25μg/kg/hour infusion). ^(b)Moderate-dose dexmedetomidine: (0.7 μg/kgbolus, 0.5 μg/kg/hour infusion). ^(c)High-dose dexmedetomidine: (1.0μg/kg bolus, 0.75 μg/kg/hour infusion). ^(d)Total dose equals the sum ofloading and maintenance doses. ^(e)Duration of total dose is the sum ofloading and maintenance dose duration. ITT = Intent-to-Treat, max =maximum, min = minimum, N = number of patients, SD = standard deviation

All 38 patients in the safety population and 36 ITT patients experiencedat least 1 treatment-emergent adverse effect during the time that thefirst dose of dexmedetomidine was administered until 24 hours hadelapsed following discontinuation of study drug administration.Thirty-three patients experienced treatment-emergent adverse effectsconsidered to be treatment-related. The SOCs with the highest incidenceof treatment-emergent adverse effects included the vascular disordersSOC (10 patients [83.3%] while receiving the low dose ofdexmedetomidine, 10 patients [83.3%] while receiving the moderate doseof dexmedetomidine, and 14 patients [100.0%] during treatment with thehigh dose of dexmedetomidine) and the metabolism and nutrition disordersSOC (10 patients [83.3%] while receiving the low dose ofdexmedetomidine, 12 patients [100.0%] while receiving the moderate doseof dexmedetomidine, and 7 patients [50.0%] while receiving the high doseof dexmedetomidine); and cardiac disorders SOC (3 patients [25.0%]during treatment with the low dose of dexmedetomidine, 4 patients[33.3%] during treatment with the moderate dose of dexmedetomidine, and4 patients [28.6%] during treatment with the high dose ofdexmedetomidine).

The majority of Treatment-emergent adverse effects were considered mildin intensity (9 patients [75.0%] for the low dose of dexmedetomidine, 9patients [75.0%] for the moderate dose of dexmedetomidine, and 7patients [50.0%] for the high dose of dexmedetomidine). A smallpercentage of Treatment-emergent adverse effects was considered moderatein intensity (2 patients [16.7%] for the low dose of dexmedetomidine, 3patients [25.0%] for the moderate dose of dexmedetomidine, and 7patients [50.0%] for the high dose of dexmedetomidine). One patient inthe low-dose dexmedetomidine treatment group experienced aTreatment-emergent adverse effect that was considered severe. Themajority of Treatment-emergent adverse effects were considereddrug-related: low-dose dexmedetomidine (11 patients, 91.7%);moderate-dose dexmedetomidine (11 patients, 91.7%); and high-dosedexmedetomidine (11 patients, 78.6%).

One hundred and seventy-one (171) treatment-emergent adverse effectswere reported by 38 patients in the Safety Population. Four patients, 3in the high dose group and 1 in the moderate dose group experienced atreatment-emergent adverse effect leading to discontinuation of studydrug. No patients discontinued study drug as a result of death. The mostcommonly reported treatment-emergent adverse effects were hyperglycemiaand hypertension. The incidence of hyperglycemia was higher with themoderate dose of dexmedetomidine compared with the low dose and highdose of dexmedetomidine (low-dose dexmedetomidine, 83.3%; moderate-dosedexmedetomidine, 100.0%; high-dose dexmedetomidine, 50.0%). Theincidence of hypertension was similar across all three dose groups ofdexmedetomidine (low-dose dexmedetomidine, 66.7%; moderate-dosedexmedetomidine, 58.3%; high-dose dexmedetomidine, 71.4%).

Study drug-related treatment-emergent adverse effect of hypertensionoccurred with the highest incidence (low-dose dexmedetomidine, 66.7%;moderate-dose dexmedetomidine, 58.3%; high-dose dexmedetomidine, 50.0%).The incidence of drug-related treatment-emergent adverse effects wassimilar across all three dose groups of dexmedetomidine. The majority oftreatment-emergent adverse effects experienced by patients in the lowand moderate dexmedetomidine dose groups were mild in intensity (lowdose, 9 patients, 75.0%; moderate dose, 9 patients, 75.0%).

A smaller percentage of patients experienced treatment-emergent adverseeffects that were moderate in intensity in the low and moderatedexmedetomidine dose groups (low dose, 2 patients, 16.7%; moderate dose,3 patients, 25.0%). A similar percentage of patients experienced bothmild and moderate treatment-emergent adverse effects in the highdexmedetomidine treatment group; 7 patients, 50.0% experienced mildtreatment-emergent adverse effects and 7 patients, 50.0% experiencedmoderate treatment-emergent adverse effects. Only one severetreatment-emergent adverse effect was reported and that was in the lowdexmedetomidine dose group.

Twenty-five patients experienced at least one treatment-emergent adverseeffect considered by the investigator to be mild during the study.Twelve patients experienced at least one treatment-emergent adverseeffect considered to be moderate, and 1 patient experienced at least onetreatment-emergent adverse effect considered to be severe in intensity.One death was reported during the study. Four patients experiencedtreatment-emergent adverse effects that led to discontinuation of studydrug.

There were no meaningful differences in clinical laboratory testresults, select vital signs (systolic blood pressure, diastolic bloodpressure, mean arterial blood pressure, body temperature, respiratoryrate), or physical examination findings between the threedexmedetomidine dose levels. Clinically significant hematologyabnormalities were observed for 1 patient (8.3%) each in the low andmoderate-dose dexmedetomidine groups (anemia) and two patients (16.7%)in the low-dose dexmedetomidine group (thrombocytopenia). With theexception of one patient in the low-dose dexmedetomidine group that hadthrombocytopenia, none of these reported adverse effects weretreatment-emergent. Greater mean change in heart rate was observed forpatients in the high-dose dexmedetomidine treatment group compared tothe other treatment groups at all time points.

The following clinically significant abnormalities in chemistrylaboratory data considered as adverse events were observed: hyperkalemia(one patient in each dose group), hypernatremia (one patient in the lowdose group), hypocalcemia (one patient in each low and moderate dosegroup), hypoglycemia (one patient each in the low and moderate dosegroups), and hypokalemia (one patient each in the low and moderate dosegroups).

Treatment-emergent adverse effects associated with vascular disordersincluded hypertension (8 patients, low dose; 7 patients, moderate dose;and 10 patients, high dose) and hypotension (5 patients, low dose; 5patients, moderate dose; and 10 patients, high dose). A statisticallysignificant treatment difference for change from Baseline for heartrate, up to and including Post Infusion Hour 5, was observed.Treatment-emergent adverse effects associated with heart rate includedtachycardia in 3 patients administered low-dose dexmedetomidine, 1patient administered moderate-dose dexmedetomidine, and 3 patientsadministered high-dose dexmedetomidine. A statistically significanttreatment difference for change from Baseline in temperature wasobserved Post Infusion Hour 28; temperature change from Baseline was−1.43±1.559° C., 0.30±0.265° C., and 1.46±1.041° C. for the low,moderate, and high dose of dexmedetomidine, respectively (p=0.008); nosignificant differences were observed at any other time point.Treatment-emergent adverse effects associated with body temperatureincluded hypothermia (1 patient, low dose and 2 patients, moderatedose), and hyperthermia (1 patient, low dose and 1 patient, high dose).No clinically meaningful changes in respiratory rate were observed andno related adverse effects were reported. No physical examinationfindings were considered clinically significant or were reported asadverse effects. ECG results were reported as adverse effects for 7patients. ECG-related adverse effects included ischemia (2 patients bothin the low dose group), ECG inverted T-wave (1 patient in the low dosegroup), elevated ST segment (1 patient in the low dose group),bradycardia (1 patient in the moderate dose group), ECG change (1patient in the high dose group), and sinus bradycardia complete heartblock (1 patient in the high dose group).

Hepatotoxicity, as defined in the SAP, was reported in 1 patient (8.3%)in the low dose group (within 24 hours of discontinuation of infusion),1 patient (8.3%) in the moderate dose group (2 to 4 weeks post-infusionor at the next follow-up visit), and 2 patients (14.3%) in the high dosegroup (within 24 hours of discontinuation of infusion); no adverseeffects related to hepatotoxicity were reported. No patients reportedDLT in this study.

Fentanyl was administered as an additional intra-operative sedationagent to patients in each dexmedetomidine dose level. The amount offentanyl administered was lower in patients receiving moderate (69.32μg), and high (80.20 μg) doses of dexmedetomidine compared to thosereceiving low (99.32 μg) levels. Post-operatively, patients wereadministered fentanyl, midazolam, and morphine sulfate. There was notreatment difference observed related to the quantity of additionalsedation received for any of the additional sedation agents. At mosttime points observed post-infusion, there was an increase in thepercentage of patients who were administered additional sedation oranalgesia for patients that received moderate levels of dexmedetomidinecompared to those who received low levels. For most time pointspost-infusion, there was a decrease in the percentage of patients thatreceived additional sedation or analgesia in the dexmedetomidine highdose level compared to those in the low dose level. There was no clearrelationship between dexmedetomidine dose level and the quantity offentanyl, midazolam, and morphine sulfate administered to patients atany post-infusion time point observed.

This was a single center, phase I dose escalation pharmacokinetic,pharmacodynamic study of a single bolus dose of dexmedetomidine followedby a continuous infusion for up to 24 hours in infants who wereimmediately post-operative from cardiac surgery and required trachealintubation with mechanical ventilation in the post-operative period.Dexmedetomidine is a highly selective alpha2 agonist with hypnotic andanxiolytic properties attributed to the alpha2A-adrenoreceptors in thelocus ceruleus. Dexmedetomidine was initially approved in 1999 for thesedation of intubated and mechanically ventilated patients in theintensive care setting for up to 24 hours, and dexmedetomidine wasrecently approved as a short term (<24 hours) sedative medication foruse in adult non-intubated patients requiring sedation prior to andduring surgical and other procedures. Thirty-eight infants, statuspost-cardiac surgery, were assigned to three treatment groups: low-dosedexmedetomidine (12 patients), moderate-dose dexmedetomidine (12patients), and high-dose dexmedetomidine (14 patients). Thirty-sixpatients, 12 in each dose group, completed the dexmedetomidine infusion.Patients were predominantly Caucasian (61.1%) with a mean age of 8.3months. Patients in the low-dose dexmedetomidine group received 0.35μg/kg bolus, 0.25 μg/kg/hour infusion, patients in the moderate-dosedexmedetomidine group received 0.7 μg/kg bolus, 0.5 μg/kg/hour infusion,and patients in the high-dose dexmedetomidine group received 1 μg/kgbolus, 0.75 μg/kg/hour infusion. Pharmacokinetic samples were collectedprior to the bolus dose through up to 18 hours after the EOI time pointsfor measurement of dexmedetomidine pharmacokinetic parameters. Therewere 36 patients in the Pharmacokinetic Population; 36 patientscompleted treatment. Sedation and analgesic properties of the drug wereto be assessed by a periodic check of the BIS monitor until afterinfusion was discontinued and the patient was deemed awake by theclinical care team. The UMSS score was also assessed on an hourly basisuntil the BIS sensor was removed.

The primary variables for pharmacokinetic assessment of dexmedetomidinewere observed peak plasma concentration (C_(max)), area under the plasmaconcentration-time curve from time zero to the last quantifiabletimepoint (AUC_(0-t)), area under the plasma concentration-time curvefrom time zero to infinity (AUC_(0-inf)), time of observed peak plasmaconcentration (T_(max)), terminal elimination rate constant (λz),terminal half-life (t_(1/2)), end of infusion concentration (steadystate C_(ss)), plasma clearance (Cl), and volume of distribution(V_(d)). Dose-proportionality was demonstrated with the analysis of meanvalues of C_(max), AUC_(0-t), and AUC_(0-inf). There was no apparentchange in clearance and weight-adjusted clearance across the age rangein this study. Pharmacodynamic assessments were monitored continuouslyevery hour until 24 hours after the discontinuation of the infusion andincluded heart rate, blood pressure, mean arterial blood pressure,cardiac rhythm, oxygen saturation, and respiratory rate. The BIS and theUMSS were used to assess the level of sedation. There were no meaningfuldifferences in systolic blood pressure, diastolic blood pressure, meanarterial blood pressure, body temperature, respiratory rate), orphysical examination findings between the 3 dexmedetomidine dose levels.Administration of a higher bolus dose resulted in a deeper level ofsedation (BIS); the change from Baseline was less for patients thatreceived the high dose of dexmedetomidine than the lower doses up to 6hours post-infusion. Of the 38 patients in the Safety Population, allpatients experienced at least 1 adverse effect that was consideredtreatment-emergent. Thirty-three patients experienced at least oneadverse effect that was considered to be treatment-related. The SOCswith the highest incidence of treatment-emergent adverse effectsincluded the vascular disorders SOC (10 patients [83.3%] while receivingthe low dose of dexmedetomidine, 10 patients [83.3%] while receiving themoderated dose of dexmedetomidine, and 14 patients [100.0%] duringtreatment with the high dose of dexmedetomidine) and the metabolism andnutrition disorders SOC (10 patients [83.3%] while receiving the lowdose of dexmedetomidine, 12 patients [100.0%] while receiving themoderate dose of dexmedetomidine, and 7 patients [50.0%] while receivingthe high dose of dexmedetomidine). In this study, no patientsexperienced a DLT.

In alignment with the primary objectives of this study, dose-dependentincreases in pharmacokinetic (mean plasma concentration, AUC_(0-t), andAUC_(0-inf)) and level of sedation were demonstrated in this study. Atmost time points investigated, no significant correlation between thelevel of sedation and serum plasma concentration, AUC_(0-t), orAUC_(0-inf) was observed for any doses tested. In addition, nocorrelation between UMSS scores and clearance of dexmedetomidine (weightadjusted and non-weight-adjusted) was observed at the majority of timepoints tested. Dexmedetomidine was generally well tolerated in infantpostoperative cardiac patients.

The following conclusions were derived regarding the administration ofdexmedetomidine for infants post-operative from cardiac surgery:

The pharmacokinetic profile demonstrated linearity and doseproportionality among 0.25, 0.50 and 0.75 μg/kg/hour dose levels; asdose increased, AUC and C_(max) increased in proportion.

Patients had deep sedation (UMSS 3-4) from pre-dose to 2 hours afterinfusion, and maintained a moderate level of sedation (UMSS 1-3) after 4hours infusion through the end of infusion for all dose levels.

There was a correlated relationship between plasma concentration andUMSS for low dose 30 minutes after start of infusion, moderate dose 8hours after end of infusion, and high dose 30-15 minutes prior to end ofinfusion and 60 minutes after end of infusion.

There was no apparent change in clearance or weight-adjusted clearanceacross the age range studied in this study.

At the majority of time points, there was no correlation observedbetween serum plasma concentration of dexmedetomidine and the level ofsedation or clearance of dexmedetomidine.

Greater mean change in heart rate was observed for patients in thehigh-dose dexmedetomidine treatment group compared to the othertreatment groups.

The doses of dexmedetomidine administered in this study were generallywell tolerated.

No clinically meaningful differences in the safety profile were observedbetween the three dose groups.

Example 6: Pooled Pharmacokinetic Data of Dexmedetomidine in PediatricPatients

The pharmacokinetic data from the Example 1 study, the Example 3 study,and the Example 5 study were pooled. Data was included for patients whoreceived treatment with dexmedetomidine and had at least 1 measurableplasma concentration with the associated dosing and sample timinginformation. For Example 1, the only subjects included were in theoriginal 30 patient population study. For Example 5, data was onlyincluded from patients who had received at least 2 hours of amaintenance infusion of dexmedetomidine and who had at least onemeasurable plasma concentration with the associated dosing and sampletiming information. A population pharmacokinetics analysis ofdexmedetomidine, including covariate assessment, was performed on thedata.

Full-profile pharmacokinetics sampling was performed in all subjects inthe Example 5 and Example 3 studies. In the Example 1 study, blood wascollected at 6 or 7 protocol-designated times for subjects based onsubject age and weight. In the Example 1 study, blood samples (0.15 mL)for pharmacokinetics analysis were collected via a central or peripheralvenous or arterial line unless access was unavailable, in which casesamples were collected from a capillary draw (heel stick). Whereappropriate, blood samples were drawn at a site opposite from the siteof infusion. Subjects in Group I who weighed less than 2 kg had blooddrawn at the end of the loading dose, 10 to 14 h after the start of themaintenance infusion, at the end of the maintenance infusion, 10 to 30minutes post-maintenance, and 3 to 4 h and 6 to 10 h post-maintenance.Subjects in Group I who weighed at least 2 kg had blood drawn at the endof the loading dose, 4 to 8 h and 10 to 14 h after the start of themaintenance infusion, at the end of the maintenance infusion, and 10 to30 minutes post-maintenance, and 1 to 2 h and 6 to 10 hpost-maintenance. Subjects in Group II had blood drawn at the end of theloading dose, 4 to 8 h after the start of the maintenance infusion, atthe end of the maintenance infusion, 10 to 30 minutes post-maintenance,and 1 to 2 h, 3 to 4 h, and 6 to 10 hrs post-maintenance.

In the Example 5 study, blood samples (1 mL) for pharmacokineticsmeasurements were drawn at a site distant from the infusion. Blood wasdrawn according to the following schedule: prior to the loading dose,0.5, 1, 2, 4 to 6 hrs after the start of the maintenance infusion, 30 to15 minutes prior to end of the maintenance infusion, and 0.25, 0.5, 1,2, 4, 8, 12, and 15 to 18 hrs after the end of the maintenance infusion.

In Study Example 3, venous blood samples (1 mL) for pharmacokineticsmeasurements were collected at a site opposite from the site ofinfusion. Blood was drawn according to the following schedule: ≤30minutes prior to the loading dose, within 5 minutes before the end ofthe loading dose, 0.5, 1, 2, 4 to 6 h after the start of the maintenanceinfusion, within 30 minutes prior to the end of the maintenanceinfusion, and 10 minutes, 0.5, 1, 2, 4, and 10 hrs after the end of themaintenance infusion.

Blood samples were collected into labeled tubes containing heparin asanticoagulant. A validated high-performance liquid chromatography-tandemmass spectrometry method for quantitation of dexmedetomidine in humanplasma was used. The lower limit of quantitation (LLOQ) was 4.24 μg/mLfor the Example 5 study, 30.24 μg/mL for Study Example 3, and 29.97μg/mL for the Example 1 study. For Study Example 3 and the Example 1study, dosing information, pharmacokinetics sampling information,dexmedetomidine concentrations, and covariate data were merged, asnecessary, to construct a time-ordered sequence of relevant events foreach subject from the start time of the first dose until the time oflast blood sample in analysis-ready datasets. Analysis-ready datasetsfor Study Example 3 and the Example 1 study were set together with thesupplemented analysis-ready dataset for the Example 5 study.

The potential of selected covariates to explain variability in thepharmacokinetics parameters for dexmedetomidine was explored. Thefollowing time-invariant (stationary) demographic and clinicalcovariates were determined at the screening visit and were assumed toremain constant for the duration of the trial:

-   -   Body weight, kg    -   Age, years    -   Alanine aminotransferase, U/L    -   Total bilirubin, mg/dL    -   Ethnicity: 1=Caucasian, 2=Black, 3=Asian, 4=Native American,        5=Hispanic, 6=other    -   Sex: 0=male, 1=female    -   Heart physiology: 0=double-ventricle, 1=single-ventricle    -   Use of concomitant glucuronidation pathway inhibitors 24 h prior        to or during surgery or during the treatment period: 0=no, 1=yes    -   Intravenous albumin infusion: 0=no, 1=yes    -   Cardio-pulmonary bypass use: 0=no, 1=yes    -   Gestational age: 1=preterm (≥28 through <36 weeks), 0=term (≥36        through <44 weeks) and    -   Site of sampling, 0=venous, 1=arterial, 2=capillary (heel        stick).

Site of sampling was recorded only in the Example 1 study and wasassumed to be venous for the studies where no information was recorded.The effect of concomitant metabolic inducers could not be explored dueto the limited timeframe for the past medication history collection asspecified in the Example 5 study (that is, 24 h prior to surgery).Aspartate aminotransferase and serum albumin data were not availablefrom the Example 5 study and were, therefore, not considered as possiblecovariates.

Although dexmedetomidine is a substrate of CYP2A6, comprehensiveliterature review regarding inhibition of CYP2A6 identified a verylimited number of commercially available drugs shown to inhibit this CYPenzyme. When the likelihood of use of these agents in a pediatricpopulation was considered, further covariate evaluation of this factorwas determined to be unnecessary.

SAS Version 9.1 or later was used for data preparation, summarystatistics, and graphical displays. Summary statistics were computed todescribe dependent and independent variables, including mean, median,standard deviation, and other measures, as appropriate. Populationpharmacokinetic modeling was performed using the computer programNONMEM®, Version VI, Level 2.0. NONMEM analyses were performed on Intelx86 computers running the OpenSUSE 10.2 distribution of Linux. TheFortran compiler used was the GNU Fortran compiler, part of the GCCVersion 3.3.5 compiler.

For each analysis, NONMEM computes the minimum value of the objectivefunction (MVOF), a statistic that is proportional to minus twice the loglikelihood of the data. In the case of hierarchical models, the changein the MVOF produced by the inclusion of a parameter is asymptoticallyχ2-distributed with the number of degrees of freedom equal to the numberof parameters added to or deleted from the model. The first-orderconditional estimation (FOCE) with interaction method was used at allstages of the model development process.

A variety of graphs and tables were generated from the analysis datasetto understand the informational content of the data with respect to theanticipated model, to search for extreme values and/or potentialoutliers, to assess possible trends in the data, and to determine if anyerrors were made in the manipulation of the data and creation of theanalysis dataset. This exploratory analysis was also used to confirm theappropriateness of the models to be tested and to verify modelassumptions. Data visualization techniques were used to search forpatterns and extreme values that may have caused significant bias duringthe analysis. An outlier was defined as an aberrant observation thatsignificantly deviated from the rest of the observations measured in aparticular subject. The general procedure that was followed for thedevelopment of the pharmacokinetics model of dexmedetomidine is outlinedbelow.

1. Exploratory data analysis.

2. Refinement of the dexmedetomidine population pharmacokinetics modeloriginally developed by Example 5 using the pooled Example 5 study dataand Study Example 3 data, including covariate analysis.

3. Further refinement of the dexmedetomidine population pharmacokineticsmodel after data from the Example 1 study became available and waspooled with the previous dataset. The influence of covariates on thepharmacokinetics parameters was re-evaluated.

4. Final model evaluation using prediction-corrected visual predictivecheck (VPC) procedure. To avoid potential multicollinearity orconfounding of effects in covariate submodels, the correlations betweencovariates were examined. Pairwise scatterplots of all continuouscovariates and boxplots of continuous covariates versus categoricalcovariates were generated. With the exception of body weight and age,which were expected to be correlated in this population, in no case were2 highly correlated covariates included in the same parameter-covariatemodel.

A linear, open, 2-compartment model for dexmedetomidine was testedinitially as a potential base structural model. This model was refinedbased on the dexmedetomidine concentration data from the Example 5 andExample 3 studies in order to determine appropriate characterization ofthe random effects. While this model included effects of body weight,age, time on CPB, and cardiac physiology (single or double ventricle) ondisposition parameters, the base structural model initially evaluatedfor this analysis did not include covariate effects unless such effectswere required to achieve model stability. It was assumed that theeffects of weight and age would be considered part of the basestructural model given the characteristics of this patient populationand their likely impact on pharmacokinetics. When the data from theExample 1 study became available, the population pharmacokinetics modelwas applied to the pooled dataset and again refined. The influence ofcovariates on the pharmacokinetics parameters was re-evaluated.

Covariate analyses were performed to explore measurable sources ofdexmedetomidine variability in pharmacokinetics model parameters withestimated interindividual variability (IIV). Table 43 lists theparameters for which the covariate effects were considered.

TABLE 43 Covariates Evaluated for Relationships With DexmedetomidineClearance and/or Volume of the Central Compartment Parameter CovariateCL Vc Body weight + + Age + + Alanine aminotransferase + Bilirubin +Ethnicity + + Sex + + Heart physiology + Glucuronidation enzymeinhibitors + Albumin infusion + + Site of sampling + + Cardiopulmonarybypass + + Abbreviations: CL, elimination clearance; Vc, volume of thecentral compartment.

Graphical and statistical approaches were used to develop the covariatemodels and to assess the mathematical forms of their relationships andtheir statistical significance. Following the development of the basestructural pharmacokinetics model, the influence of covariates onselected pharmacokinetics parameters for dexmedetomidine was evaluatedunivariately. Diagnostic plots illustrating the relationships betweenthe unexplained IIV in CL and Vc and covariates were examined toidentify possible trends, as well as the appropriate functional form(for example, linear, power, or exponential) to be tested for theparameter-covariate relationship. Covariates contributing at least a3.84 change in the MVOF (α=0.05, 1 degree of freedom forχ2-distribution) and a 5% reduction in IIV in the parameter of interestwere included in the model and the process was repeated. The errormodels for IIV in the full multivariable model were re-evaluatedfollowing completion of forward selection.

Univariate backward elimination proceeded after all adjustments had beenmade to the error models. A covariate was considered significant andkept in the model if it contributed at least a 10.83 change in the MVOF(α=0.001, 1 degree of freedom for χ2-distribution) when removed from themodel. The reduced multivariable model, with all significant covariates,was evaluated for any remaining biases in the IIV and residualvariability (RV) error models. Diagnostic plots of the unexplained IIVin the parameters versus all covariates were evaluated to detect anyinadequacies or biases in the covariate models and to assure no trendsremain that may indicate a potential relationship had not beensufficiently described by the model. The model was checked for possiblesimplifications of covariate equations, such as power functions that canbe reduced to linear functions (power term approximately 1.0) orsignificant discrete group covariates that could be redefined usingfewer groups or parameters. Goodness-of-fit diagnostic plots wereexamined for model misfit.

The adequacy of the final model was evaluated using a simulation-basedprediction corrected VPC method. The final model was used to simulate1000 replicates of the analysis dataset with NONMEM. Statistics ofinterest were calculated from the simulated and observed data forcomparison; for example, the 5th, 50th (median), and 95th percentiles ofthe distributions of the dexmedetomidine concentrations within discretebins (ranges) of time, treatment group, and age were calculated. Thesepercentiles of the simulated concentrations were then plotted versustime since the end of the maintenance infusion, with the originalobserved dataset and/or percentiles based on the observed data overlaidto visually assess concordance between the model-based simulated dataand the observed data.

Due to the wide range of doses used in these studies and the spectrum ofsubjects with regard to age (and weight), the prediction-corrected VPC,as suggested by Bergstrand, et al, with bins defined by time, treatmentgroup, and age, was utilized. (See AAPS J. 2011; 13(2):143-151). Thistechnique provides an enhanced ability to diagnose possible modelmisspecification by removing the variability introduced in an ordinaryVPC when binning across a potentially large variability in dose or otherinfluential covariates. A total of 1448 dexmedetomidine concentrationrecords from 131 subjects and 3 studies were received. After exclusions,1279 dexmedetomidine concentrations collected from 120 subjects in thesestudies were available for analysis (Table 44).

TABLE 44 Data Disposition for Each Study Included in the PopulationPharmacokinetic Analysis Number Remaining Samples Subjects SubjectsFollowing the Excluded Excluded Affected Excluded Samples SubjectsExample 1 Study Dexmedetomidine NA NA NA NA 37 randomized subjectsRandomized subjects with no  0 2 2 NA 34 concentration recordsDexmedetomidine concentration NA NA NA 228 34 records received fromHospira, Inc. Missing concentration values 28 8 4 200 30 Allconcentrations below lower limit 27 4 4 173 26 of quantitation Sub-totalprior to outlier exclusions NA NA NA NA NA Improbable concentrationsbased on 17 5 2 156 24 EDA plots^(a) Observations associated with  3 2 0153 24 extremely high weighted residual values during modeldevelopment^(a) Total remaining NA NA NA 153 24 Example 5 StudyDexmedetomidine randomized NA NA NA NA 36 subjects Dexmedetomidineconcentration NA NA NA 479 NA records received from Hospira, Inc.Concentrations below lower limit of 36 36  0 443 36 quantitationSub-total prior to outlier exclusions NA NA NA 443 36 Observationsassociated with  5 4 0 438 36 weighted residual values >7 during basemodel development^(a) Subjects with extremely long bypass 11 1 1 427 35time^(a,b) Total remaining NA NA NA 427 35 Example 3 StudyDexmedetomidine randomized NA NA NA NA 59 subjects Dexmedetomidineconcentration Na  NA NA 741 NA records received from Hospira, Inc.Missing concentration value  9 6 0 732 59 Pre-dose concentrations belowlower 57 57  0 675 59 limit of quantitation All concentrations belowlower limit 12 1 1 663 58 of quantitation Sub-total prior to outlierexclusions NA NA NA 663 58 Extremely high concentrations noted  4 2 0659 58 during EDA^(a) Observations associated with 23 16  0 636 58weighted residual values >7 during base model development^(a) Subjectsexcluded from analysis due  9 3 3 627 55 to infusion length shorter thanallowed per protocol or lack of samples collected^(a) Implausibleconcentration value^(a)  1 1 0 626 55 Subject to extremely high CLvalue^(a) 11 1 1 615 54 Total remaining NA NA NA 615 54 Total prior tooutlier exclusions^(a) NA NA NA 1279  120  Total for pooled data NA NANA 1195  113  Abbreviations: EDA, exploratory data analysis; NA, notapplicable. ^(a)Note: Rows representing observations designated asoutliers. ^(b)Su F, Nicolson S C, Gastonguay M R, et al. Populationpharmacokinetics of dexmedetomidine in infants after open heart surgery.Anesth Analog. 2010; 110(5): 1383-1392.

Table 45 summarizes the numbers of subjects and dexmedetomidineconcentration values included in the analysis, by study and randomizedtreatment group.

TABLE 45 Summary of the Numbers of Subjects and DexmedetomidineConcentrations, by Study and Dexmedetomidine Treatment GroupDexmedetomidine Treatment Group (Loading Number of Dose + MaintenanceNumber of Concen- Study Infusion Rate) Subjects trations Example 1 0.05μg/kg + 0.05 μg/kg/h 10 63 0.10 μg/kg + 0.10 μg/kg/h 8 55 0.20 μg/kg +0.20 μg/kg/h 8 55 Subtotals for 26 173 Example 1 Example 5 0.35 μg/kg +0.25 μg/kg/h 12 139 0.70 μg/kg + 0.50 μg/kg/h 12 152 1.00 μg/kg + 0.75μg/kg/h 12 152 Subtotals for 36 443 Example 5 Example 3 0.25 μg/kg +0.20 μg/kg/h 15 169 0.50 μg/kg + 0.40 μg/kg/h 14 159 1.00 μg/kg + 0.70μg/kg/h 15 167 1.00 μg/kg + 2.00 μg/kg/h 14 168 Subtotals for 58 663Example 3 Overall 120 1279

Subject demographic characteristics, overall and by study, are shown inTable 46.

TABLE 46 Summary of Demographic Characteristics, by Study Example 1Example 5 Example 3 Subject Characteristic Study Study Study Overall Age(y) Mean (SD) 0.041 (0.029) 0.716 (0.404) 7.397 (4.193) 3.799 (4.555)Median    0.036    0.631    6.702    1.560 Min, Max 0.01, 0.13 0.21,2.65  2.07, 16.97 0.01, 16.97 n 26 36 58 120 Weight (kg) Mean (SD) 2.905(0.879) 7.625 (1.802) 27.320 (20.140) 16.122 (17.791) Median    3.165   7.040    20.250    10.350 Min, Max 1.12, 4.35 5.10, 11.90 9.98, 99.001.12, 99.00 n 26 36 58 120 Ethnicity, n White 20 (76.9) 23 (63.9) 23(39.7) 66 (55.0) (%) Black 9 (25.0) 9 (25.0) 6 (10.3) 15 (12.5) Asian 1(2.8) 1 (2.8) 1 (2.8) 1 (0.8) American 0 (0.0) 0 (0.0) 0 (0.0) 1 (0.8)Indian 2 (5.6) 2 (5.6) 2 (5.6) 32 (26.7) Hispanic 1 (3.8) 1 (2.8) 1(2.8) 5 (4.2) Other Gender, n (%) Male 19 (73.1) 20 (55.6) 27 (46.6) 66(55.0) Female 7 (26.9) 16 (44.4) 31 (53.4) 54 (45.0)

Overall, slightly more than one-half of the subjects were male (55%),with a median age of 1.56 years (range of 0.01 to 16.97 years) and amedian weight of 10.35 kg (range of 1.12 to 99 kg). The majority of thesubjects were Caucasian (55%). For the most part, the ranges of age andweight represented in the 3 studies comprise a continuum of maturationand size from very small infants to nearly adults with little or nooverlap in these characteristics between studies. As shown in Table 47,the median alanine aminotransferase level was 21.0 U/L for the subjectsoverall, with a slightly higher median in the Example 5 subjects (24.0U/L) compared to the median values in the Example 3 (19.0 U/L) andExample 1 (19.5 U/L) subjects. The median value for total bilirubin inthe overall group was 0.5 mg/dL; although, total bilirubin levels wereconsiderably higher in the Example 1 subjects (median total bilirubinlevel of 4.65 mg/dL).

TABLE 47 Summary of Laboratory Values, by Study Study Example 5 StudySubject Characteristic Example 1 Study Example 3 Overall Alanine Mean(SD) 27.077 (22.337) 25.917 (8.917) 26.828 (21.881) 26.608 (18.914)aminotransferase Median 19.500 24.000 19.000 21.000 (U/L) Min, Max 7.00,84.00 8.00, 52.00 9.00, 144.00 7.00, 144.00 n 26 36 58 120 Totalbilirubin Mean (SD) 4.871 (3.708) 0.347 (0.146)  0.591 (0.425) 1.445(2.503) (mg/dL) Median 4.650 0.300 0.500 0.500 Min, Max 0.20, 14.600.10, 0.70  0.17, 2.20  0.10, 14.60  n 27 36 58 120

Table 48 shows the summary statistics for cardiac status of the subjects(cardio-pulmonary bypass and heart ventricle physiology), administrationof albumin infusion or medications known to be glucuronidation pathwayinhibitors, and site of blood sampling for pharmacokinetics analysis ofdexmedetomidine concentrations.

TABLE 48 Summary of Cardiac Status, Concomitant Medications, and Site ofPharmacokinetic Sampling Study Example 5 Study Subject CharacteristicExample 1 Study Example 3 Overall Cardio-pulmonary bypass, n No 21(80.8) 0 (0.0) 17 (29.3) 38 (31.7) (%) Yes 5 (19.2) 36 (100.0) 41 (70.7)82 (68.3) Ventricle, n (%) Single 0 (0.0) 19 (52.8) 0 (0.0) 19 (15.8)Double 26 (100.0) 17 (47.2) 58 (100.0) 101 (84.2) Albumin infusion, n(%) No 19 (73.1) 36 (100.0) 46 (79.3) 101 (84.2) Yes 7 (26.9) 0 (0.0) 12(20.7) 19 (15.8) Glucuronidation pathway No 6 (23.1) 0 (0.0) 7 (12.1 13(10.8) inhibitors, n (%) Yes 20 (76.9) 36 (100.0) 51 (87.9) 107 (89.2)Site of sampling^(a) Venous 66 (38.2) 443 (100.0) 663 (100.0) 1172(91.6) Arterial 95 (54.9) 0 (0.0) 0 (0.0) 95 (7.4) Capillary 12 (6.9) 0(0.0) 0 (0.0) 12 (0.9)

All Example 5 subjects and most Example 3 subjects (70.7%) underwentcardio-pulmonary bypass, but relatively fewer subjects in the Example 1study (19.2%) underwent this procedure. Subjects with single ventriclephysiology were only present in the Example 5 study (52.8%). Overall,the majority of subjects (84.2%) did not receive an albumin infusion,and 89.2% of subjects received co-medications known to beglucuronidation pathway inhibitors 24 h prior to surgery, duringsurgery, or during dexmedetomidine treatment.

Plasma samples for the determination of dexmedetomidine concentrationswere collected around the time of the loading dose, near the start andduring the maintenance infusion, and after discontinuation of themaintenance infusion according to the pre-specified schedules for thestudies in Examples 1, 3, and 5. The number of plasma dexmedetomidineconcentrations contributed per individual subject ranged from 1 to 13across studies with the most samples per subject in Example 5 (10 to 13,median of 13), a similar amount per subject in Example 3 (1 to 12,median of 12), and less from Example 1, as expected (5 to 7, median of 7samples per subject). The overall range of dexmedetomidine doses forboth the loading dose and maintenance infusion was large (56 ng to140,000 ng and 357 ng to 828,800 ng, respectively). Summary statisticsfor the dexmedetomidine loading doses and maintenance infusion doses areshown in Tables 5A, 27A, and 37.

Looking across all of the treatment groups, the median totaldexmedetomidine doses for the Example 1, 3, and 5 studies were 2184 ng,36,011 ng, and 120,550 ng, respectively. The infusion durations for theloading dose (median of 0.167 h in almost all treatment groups) andmaintenance doses (median ranged from approximately 6 h to 9 h in almostall treatment groups) were quite consistent across the studies.

FIGS. 16A-C present lineplots of plasma dexmedetomidine concentrationsversus time since the start of the loading dose infusion for eachtreatment group in the 3 studies. In FIGS. 17A-C, lineplots ofdexmedetomidine concentrations versus time since the end of themaintenance infusion are shown for each treatment group. Based on theconcentrations measured after the end of the infusion, these plotssuggest that a 2-compartment model would likely be adequate to describethese data. Although this finding is consistent with a previous reportdescribing the population pharmacokinetics for dexmedetomidine ininfants, other types of models were additionally examined.

FIGS. 18A-B show a semilogarithmic scatterplot of dose-normalizeddexmedetomidine plasma concentrations versus time since the end of themaintenance infusion stratified by study, demonstrating thatdexmedetomidine pharmacokinetics was generally similar across thetreatment groups from the Example 3 and Example 5 studies. Smoothingsplines are used in these plots to illustrate the trend over time withineach treatment group. There appears to be a trend towards higherdose-normalized dexmedetomidine concentrations in the lowest dose group(0.05 mg/kg+0.05 mg/kg/h) from the Example 1 study, however, the patternis less evident in the 0.10 mg/kg+0.10 mg/kg/h and 0.20 mg/kg+0.20mg/kg/h dose groups.

The percent of BLQ samples within the Example 5 and Example 3 studieswere quite similar (slightly less than 10% in each study and 3% and 5%overall, respectively), although the percent of samples that were BLQwas much higher in the Example 1 study (approximately 40% of the studyand 5% overall). The BLQ samples were retained in the dataset and set toa value of one-half the LLOQ of the assay used to determine thedexmedetomidine concentration in the particular study.

The pooled data from Studies Example 3 and Example 5 were initially usedfor model development. Based on previous modeling efforts and theexploratory analysis results (in particular, the scatterplots ofdexmedetomidine concentrations versus time), a 2-compartment model, aswell as 1- and 3-compartment linear models, were fit to the data. (SeeSu et al.) A mammillary 2-compartment model best described the data,with IIV estimated on CL, Vc, Q, and volume of the Vp using exponentialerror models. Residual variability was estimated separately for eachstudy using a combined additive and constant coefficient of variationerror model.

Based on literature recommendations, fixed allometric exponents forscaling of body weight were included for the clearance and volumeparameters (0.75 for CL and Q and 1.0 for Vc and Vp). These standardexponents predict a less than proportional increase in CL and Q withincreasing body weight and a proportional increase in Vc and Vp withincreasing body weight. A negative linear relationship between and ageand Vp, as well as a negative power function to relate age and Q, werealso included in the base structural pharmacokinetic model describingthe data from these 2 studies.

Pharmacokinetic parameter estimates and standard errors of the estimatesfor the fit of the 2-compartment model to these data are presented inTable 49.

TABLE 49 Parameter Estimates and Standard Errors From theDexmedetomidine Pharmacokinetic Model Developed Using Example 5 andExample 3 Data Only Magnitude of Final Parameter InterindividualEstimate Variability (% CV) Population % Final % Parameter Mean SEMEstimate SEM CL (L/h)^(a) 18.5 3.5 30.76 18.3 Vc (L)^(b) 18.9 8.9 68.2617.0 Intercompartmental 35.9 15.8 CL (L/h)^(c) Exponent of power −0.50933.6 117.05 24.9 relationship between Q and age^(c) Vp (L)^(d) 19.1 9.3Slope of linear age −1.43 15.3 27.15 56.7 effect on Vp (L/y)^(d) Ratioof additive to 11.8 14.7 NA NA proportional RV: Example 5 Ratio ofadditive to 42.1 15.5 NA NA proportional RV: Example 3 RV Example 5^(e)0.0363 16.9 NA NA RV Example 3^(f) 0.0712 19.1 NA NA Minimum value ofthe objective function = 9930.466 Abbreviations: CL, eliminationclearance; IIV, interindividual variability; NA, not applicable; % CV,coefficient of variation expressed as a percentage; % SEM, standarderror of the mean expressed as a percentage; Q, intercompartmentalclearance; RV, residual variability; Vc, volume of the centralcompartment; Vp, volume of the peripheral compartment; WTKG, weight inkg.${\;^{a}{Typical}\mspace{14mu}{CL}} = {18.5 \times \left( \frac{WTKG}{1{9.8}} \right)^{0.75}}$${\;^{b}{Typical}\mspace{14mu}{Vc}} = {18.9 \times \left( \frac{WTKG}{1{9.8}} \right)}$${\;^{c}{Typical}\mspace{14mu} Q} = {35.9 \times \left( \frac{WTKG}{1{9.8}} \right)^{0.75} \times \left( \frac{age}{4.8} \right)^{- 0.509}}$${\;^{d}{Typical}\mspace{14mu}{Vp}} = {{19.1 \times \left( \frac{WTKG}{1{9.8}} \right)} - {1.43 \times \left( {{age} - 4.8} \right)}}$^(e)Residual variability estimate is expressed as a variance. Thecorresponding % CV for RV in Example 5 ranges from 108% CV at 2.12 ng/L(one-half the lower assay limit) to 19% CV at 700 ng/L. ^(f)Residualvariability estimate is expressed as a variance. The corresponding % CVfor RV in Example 3 ranges from 79% CV at 15.12 ng/L (one-half the lowerassay limit) to 27% CV at 2000 ng/L.

Most parameters were estimated with reasonable precision (standard errorof the mean expressed as a percentage [% SEM]<34%), with the exceptionof the IIV for Vp, which was estimated with slightly poorer precision (%SEM=56.7%). Diagnostic plots indicated a good fit to the data, with noapparent biases, except a slight degree of under-prediction ofconcentrations measured more than 10 h after the end of the infusion.This under-prediction may be due to the prediction of late samples atlevels below the limit of quantitation of the assay, where the observeddata were fixed to values of one-half the assay limit.

Model development was continued with the addition of the Example 1 datato the pooled Example 3 and Example 5 dataset. When the model developedusing the Example 5 and Example 3 data was applied to the pooled datasetincluding Example 1, high correlations were initially observed betweenmany of the parameters. Due to the difference in weight and age of thesubjects from Example 1 as compared to the older subjects from the othertwo studies, the model including only the allometric functions of weightwas evaluated next, removing the additional effects of age that wereincluded in the previous model. After refining this model with thepooled dataset first, the effect of maturation on variouspharmacokinetics parameters was then addressed.

In the evaluation of maturation effects on dexmedetomidinepharmacokinetics, shifts in the allometric exponents were tested forpre-term subjects (that is, those with gestational age ≤28 weeks fromExample 1), as well as neonates (that is, subjects less than 1 month ofage, regardless of gestational age) as compared to all other subjects.Shifts in the allometric exponents for CL and Vc for neonates wereassociated with the largest reduction in the MVOF (approximately 48points) and good precision of parameter estimates and were, therefore,retained in the model. Both Q and Vp were additionally found to bestatistically significantly related to age. A power function was used todescribe the negative relationships between these parameters and age(that is, both parameters decrease with increasing age).

The final base structural pharmacokinetics model for the pooled datasetof Examples 1, 3, and 5 was a 2-compartment model with IIV estimated onCL, Q, Vc, and Vp using exponential error models, separate additive andconstant coefficient of variation RV models for each study, fixedallometric exponents (as stated above) on the clearance and volumeparameters with an additional shift on the CL and Vc exponents forneonates, age effects on Q and Vp described by power functions (bothdecrease with increasing age), and covariance parameters for the IIVs onCL and Vp, and the IIVs on Q and Vc. The final base structural2-compartment model and standard errors are presented in Table 50.

TABLE 50 Parameter Estimates and Standard Errors From theDexmedetomidine Base Structural Magnitude of Interindividual FinalParameter Variability Estimate (% CV) Population % Final % ParameterMean SEM Estimate SEM CL (L/h)^(a) 11.5 3.5 Proportional shift in 0.48020.88 35.07 17.2 allometric exponent for CL for neonates^(a) Vc (L)^(b)9.46 11.4 Proportional shift in 0.513 56.7 53.48 21.6 allometricexponent for Vc for neonates^(b) Intercompartmental CL 71.0 41.4(L/h)^(c) Exponent for power −0.286 37.8 164.32 34.3 function effect ofage on Q^(c) Vp (L)^(d) 15.2 8.8 Exponent for power −0.291 12.2 47.1223.3 function effect of age on Vp^(d) Ratio of additive to 8.73 40.3 NANA proportional RV: Example 1 Ratio of additive to 12.3 14.4 NA NAproportional RV: Example 5 Ratio of additive to 40.8 16.8 NA NAproportional RV: Example 3 cov(IIV in CL, IIV in Vp) 0.124 21.5 NA NAcov(IIV in Q, IIV in Vc) 0.814 22.6 NA NA RV Example 1^(e) 0.194 22.6 NANA RV Example 5^(f) 0.0359 16.4 NA NA RV Example 3^(g) 0.0684 18.7 NA NAMinimum value of the objective function = 11069.294 Abbreviations: CL,elimination clearance; IIV, interindividual variability; NA, notapplicable; NEO, indicator variable for neonates; % CV, coefficient ofvariation expressed as a percentage; % SEM, standard error of the meanexpressed as a percentage; Q, intercompartmental clearance; RV, residualvariability; Vc, volume of the central compartment; Vp, volume of theperipheral compartment; WTKG, weight in kg.${\;^{a}{Typical}\mspace{14mu}{CL}} = {11.5 \times \left( \frac{WTKG}{10.35} \right)^{\lbrack{0.75 \times {({1 + {0.480\; \times {NEO}}})}}\rbrack}}$${\;^{b}{Typical}\mspace{14mu}{Vc}} = {9.46 \times \left( \frac{WTKG}{10.35} \right)^{\lbrack{1 + {0.513\; \times {NEO}}}\rbrack}}$${\;^{c}{Typical}\mspace{14mu} Q} = {71.0 \times \left( \frac{WTKG}{10.35} \right)^{0.75} \times \left( \frac{age}{1.56} \right)^{- 0.286}}$${\;^{d}{Typical}\mspace{14mu}{Vp}} = {15.2 \times \left( \frac{WTKG}{10.35} \right) \times \left( \frac{age}{1.56} \right)^{- 0.291}}$^(e)Residual variability estimate is expressed as a variance. Thecorresponding % CV for RV in Example 1 study ranges from 51% CV at 14.97ng/L (one-half the lower assay limit) to 44% CV at 200 ng/L.^(f)Residual variability estimate is expressed as a variance. Thecorresponding % CV for RV in Example 5 study ranges from 112% CV at 2.12ng/L (one-half the lower assay limit) to 19% CV at 700 ng/L.^(g)Residual variability estimate is expressed as a variance. Thecorresponding % CV for RV in Example 3 study ranges from 75% CV at 15.12ng/L (one-half the lower assay limit) to 26% CV at 3000 ng/L.

With the exception of the parameter for the proportional shift in theallometric exponent for Vc for neonates (% SEM of 56.7%), the otherfixed and random effect model parameters were all estimated withreasonable precision (most % SEMs <40%). Goodness-of-fit plots are shownin FIGS. 19A-B for the base structural model for the pooled dataset ofExamples 1, 3, and 5. Diagnostic plots indicate a good fit to the pooleddata and a lack of substantial bias.

The following covariates were tested on CL and Vc: gender, ethnicity,cardio-pulmonary bypass use, albumin infusion (presence), and site ofsampling (arterial versus venous versus capillary). The followingcovariates were tested on CL only: alanine aminotransferase, totalbilirubin, glucuronidation pathway inhibitors (presence), and heartphysiology (single versus double ventricle). The effect of ethnicity wasmodeled as Caucasian versus Hispanic versus all “other” race groups(Asian, black) that were combined due to the small sample sizes. Eachcontinuous covariate effect was tested in NONMEM using a linear andpower model. Categorical covariates were tested using additive shifts.Delta-parameter plots were generated to illustrate the possiblerelationships between the remaining unexplained IIV in CL or Vc and thecovariates of interest. No obvious trends are apparent indicating likelyparameter-covariate relationships. Furthermore, the lack of trend in theplots for age and weight indicate that these factors are adequatelyaccounted for in the base structural model, which includes allometricweight relationships and additional effects of maturation. Although theeffect of several covariates (total bilirubin, albumin infusion, andalanine aminotransferase on CL) was statistically significant (P value<0.05 based on a reduction in the MVOF following their inclusion in themodel), none of these covariate effects was also associated with a ≥5%reduction in IIV in CL.

As a result of the univariate forward selection results, no additionalcovariates were added to the base model. Therefore, the backwardelimination step was not performed and this base model was nextevaluated for further refinement and simplification. Next, the basestructural model following forward selection was checked for possiblesimplifications in an effort to identify the most appropriate andparsimonious model which adequately characterized these data. Removal ofthe shift for the allometric exponent on Vc for neonates resulted in anon-statistically significant increase in the MVOF of 1.991 (Pvalue >0.05) and was, therefore, removed from the model. Furthersimplification of the RV model for Example 1 to a constant coefficientof variation error model was also performed; this simplification wasalso associated with a non-statistically significant increase in theMVOF of 1.331 (P value >0.05) and was, therefore, implemented.

Goodness-of-fit diagnostic plots were examined for model misfit. Severalalternative methods for handling of BLQ samples were also evaluated,including Beals M3 method and the exclusion of BLQ samples after thefirst one in a sequence, but these attempts did not minimizesuccessfully or did not result in model improvement. A furtherassessment of the model including all outliers did not result insuccessful minimization; therefore, the observations identified asoutliers during model development were permanently excluded. Asimulation-based prediction-corrected VPC was performed using the finalpharmacokinetics model, simulating 1000 replicates of the analysisdataset. This VPC method was used to improve the ability to diagnosepossible model misspecification by removing the variability resultingfrom the broad range of doses and ages/weights of subjects. Therefore,for the purposes of the prediction correction, discrete bins based ontime since the end of the infusion, dexmedetomidine treatment group, andage were defined.

FIG. 20 illustrates the 90% prediction interval, derived from the 1000simulated datasets, overlaid on the observed dexmedetomidineconcentrations versus time since the end of the maintenance infusion.Concentrations measured prior to the end of the maintenance infusion arepresented with a negative value for the time since the end of themaintenance infusion. The majority of the observed data falls within theprediction interval. The percentage of the observed concentrations belowthe 5th percentile was 6.3% and the percentage above the 95thpercentiles was 4.7%. The VPC indicates no apparent biases in theoverall model fit by comparing the simulated data (based on the model)to the raw data.

FIG. 21 illustrates a comparison of the 5th, 50th, and 95th percentileof the prediction-corrected observed and model-based simulated data.This plot also confirms the high degree of concordance between thesimulation-based data and the observed data, wherein the 50thpercentiles of the observed and simulated data track very well acrossthe entire range of time. For the purposes of the VPC, the simulatedconcentrations were treated in a manner identical to the observedconcentrations, whereby values less than the assay limit for the studywere set to one-half the appropriate limit.

The final population pharmacokinetics model was a 2-compartment modelwith IIV estimated on CL, Q, Vc, and Vp using exponential error models,fixed allometric exponents on the clearance (0.75 for CL and Q) andvolume of distribution (1.0 for Vc and Vp) parameters, with anadditional shift on the CL exponent for neonates, age effects on Q andVp described by power functions (both decrease with increasing age),covariance terms for the IIVs on CL and Vp, and the IIVs on Q and Vc,separate additive plus constant coefficient of variation error modelsfor Studies Example 3 and Example 5, and a constant coefficient ofvariation error model for the Example 1 study.

The parameter estimates for the final population pharmacokinetics modelfor dexmedetomidine are provided in Table 51.

TABLE 51 Parameter Estimates and Standard Errors From theDexmedetomidine Final Population Pharmacokinetic Model Magnitude ofInterindividual Final Parameter Variability Estimate (% CV) Population %Final % Parameter Mean SEM Estimate SEM CL (L/h)^(a) 11.4 3.5 17.3Proportional shift in 0.468 19.3 35.07 allometric exponent for CL forneonates^(a) Vc (L)^(b) 9.20 11.6 54.13 21.6 Intercompartmental CL 70.543.7 37.3 (L/h)^(c) Exponent for power −0.293 39.6 163.40 functioneffect of age on Q^(c) Vp (L)^(d) 15.2 8.8 24.3 Exponent for power−0.282 12.9 47.33 function effect of age on Vp^(d) Ratio of additive to8.79 15.8 NA NA proportional RV: Example 5 Ratio of additive to 27.454.4 NA NA proportional RV: Example 3 cov(IIV in CL, IIV in Vp) 0.12422.8 NA NA cov(IIV in Q, IIV in Vc) 0.818 23.6 NA NA RV Example 1^(e)0.214 20.4 NA NA RV Example 5^(f) 0.0358 16.4 NA NA RV Example 3^(g)0.0682 18.8 NA NA Minimum value of the objective function = 11072.619Abbreviations: CL, elimination clearance; IIV, interindividualvariability; NA, not applicable; NEO, indicator variable for neonates; %CV, coefficient of variation expressed as a percentage; % SEM, standarderror of the mean expressed as a percentage; Q, intercompartmentalclearance; RV, residual variability; Vc, volume of the centralcompartment; Vp, volume of the peripheral compartment; WTKG, weight inkg.${\;^{a}{Typical}\mspace{14mu}{CL}} = {11.4 \times \left( \frac{WTKG}{10.35} \right)^{\lbrack{0.75 \times {({1 + {0.468\; \times {NEO}}})}}\rbrack}}$${\;^{b}{Typical}\mspace{14mu}{CL}} = {9.20 \times \left( \frac{WTKG}{10.35} \right)}$${\;^{c}{Typical}\mspace{14mu}{CL}} = {70.5 \times \left( \frac{WTKG}{10.35} \right)^{0.75} \times \left( \frac{age}{1.56} \right)^{- 0.293}}$${\;^{d}{Typical}\mspace{14mu}{Vp}} = {15.2 \times \left( \frac{WTKG}{10.35} \right) \times \left( \frac{age}{1.56} \right)^{- 0.282}}$^(e)Residual variability estimate is expressed as a variance. Thecorresponding % CV for RV in Example 1 is 46% CV. ^(f)Residualvariability estimate is expressed as a variance. The corresponding % CVfor RV in Example 5 ranges from 111% CV at 2.12 ng/L (one-half the lowerassay limit) to 19% CV at 700 ng/L. ^(g)Residual variability estimate isexpressed as a variance. The corresponding % CV for RV in Example 3ranges from 75% CV at 15.12 ng/L (one-half the lower assay limit) to 26%CV at 3000 ng/L.

All fixed effect parameters were estimated with good precision (% SEMs<20%), with the exception of those associated with Q, which wereestimated with slightly poorer precision (% SEMs of around 40%). Randomeffects were also estimated with good precision (most % SEMs <25%,except IIV in Q with % SEM=37%). Interindividual variability in CL, Vc,and Vp was moderate, ranging from 35% CV to 55% CV. Unexplained IIV in Qwas very high at 163% CV. Overall, RV was the lowest in the Example 5data (around 19% CV) and slightly higher in the Example 3 data (26% CV),but in both studies was considerably larger at low of variation RV modelwas found to adequately describe the data from Example 1, with arelatively higher estimate of 46% CV, regardless of concentration level.

The equations describing the relationships between the typicaldexmedetomidine parameter values and the subject factors included in themodel (that is, those relating to weight and age) are provided inEquation 1, Equation 2, Equation 3, and Equation 4.

$\begin{matrix}{{{Typical}\mspace{14mu}{CL}_{j}} = {11.4 \times \left( \frac{{WTKG}_{j}}{10.35} \right)^{\lbrack{0.75{x{({1 + {0.468 \times {NEO}_{j}}})}}}\rbrack}}} & (1) \\{{{Typical}\mspace{14mu}{Vc}_{j}} = {9.20 \times \left( \frac{{WTKG}_{j}}{10.35} \right)}} & (2) \\{{{Typical}\mspace{14mu} Q_{j}} = {70.5 \times \left( \frac{{WTKG}_{j}}{10.35} \right)^{0.75} \times \left( \frac{{age}_{j}}{1.56} \right)^{- 0.293}}} & (3) \\{{{Typical}\mspace{14mu}{Vp}_{j}} = {15.2 \times \left( \frac{{WTKG}_{j}}{10.35} \right) \times \left( \frac{{age}_{j}}{1.56} \right)^{- 0.282}}} & (4)\end{matrix}$

Where.

CL_(j) is the typical value of dexmedetomidine clearance in the jthsubject predicted by the model,

Vc_(j) is the typical value of dexmedetomidine volume of the centralcompartment in the jth subject predicted by the model,

Q_(j) is the typical value of dexmedetomidine intercompartmentalclearance in the jth subject predicted by the model,

Vp_(j) is the typical value of dexmedetomidine volume of the peripheralcompartment in the jth subject predicted by the model,

age_(j) is the age, in years, of the jth subject,

WTKG_(j) is the weight, in kg, of the jth subject, and

NEO_(j) is an indicator variable with a value of 1 for neonate subjectsand 0 otherwise.

Goodness-of-fit plots for this model are provided in FIGS. 22A-D for theentire population. At the level of the overall dataset, these diagnosticplots indicate a reasonably unbiased fit of the model to the dataset,with a slight underprediction of the samples collected more than 10 hafter the end of the infusion. This is apparent in the grouping ofpoints that are associated with positive weighted residuals after 10 hin the plot of weighted residuals versus time since end of the infusion.In addition, these plots provide support for the selected models for RVbased on the lack of trend or pattern in the plots of individualweighted residuals versus individual predicted concentrations. Tofurther illustrate the appropriateness of the model across the treatmentgroups and age range of the subjects, additional goodness-of-fit plotswere prepared stratified by treatment group and by age group. Althoughsome treatment and age groups represent very small sample sizes, theseplots indicated no substantial persistent trends of misfit or biasacross the range of doses or age levels. Calculations of the shrinkageof the empirical Bayesian estimate distributions indicate no concernover excessive shrinkage for any of the pharmacokinetics parameters asthe estimates are all indicative of low shrinkage (that is, 3.5% for CL,13.7% for Vc, 13.7% for Q, and 12.6% for Vp).

Pairwise scatterplots of these terms are provided in FIG. 25. Theseplots demonstrate the modeled correlations between the IIV in CL and Vpand between the IIV in Q and Vc, as well as a lack of substantialrelationship between other pairs of terms.

The final base structural pharmacokinetics model for dexmedetomidineusing the pooled data from the 3 studies was a 2-compartment model withfixed allometric exponents on the clearance and volume parameters, anadditional shift on the CL and Vc exponents for neonates, and ageeffects on Q and Vp. The allometric weight adjustments using the fixedcoefficients of 0.75 for CL and 1 for volume terms were based on awell-described scientific framework that can be related to basicphysiologic functions, and have been used frequently in pediatricpharmacokinetics analyses. Because the allometric coefficients werefixed for maturation based on age could be delineated from the effect ofsize. With the inclusion of the Example 1 study data in the analysis,the shifts on CL and Vc were included for the neonate group to correctfor maturation only in these youngest subjects. In addition, the ageeffects on Q and Vp (decrease with increasing age) were included in themodel for all subjects, and are consistent with known age-dependentchanges in proportions of body water and fat which influence thedistribution of drugs. Overall, this covariate approach avoided problemswith co-linearity between size and age by first addressing size as afixed allometric exponent, and then using age to describe maturation, ashas been previously suggested in the literature.

Additional covariate effects were tested on dexmedetomidine CL and Vcbased on clinical interest and physiologic plausibility; however, noeffect met the pre-specified criteria for inclusion in the model. In apreviously developed 2-compartment population pharmacokinetics model ofdexmedetomidine in infants (aged 1 to 24 months) after open heartsurgery, significant covariate effects included total bypass time on CLand Vc and ventricular physiology (1- or 2-ventricle) on CL, in additionto fixed allometric effects of weight on CL, Q, Vc, and Vp. There areseveral factors that may contribute to the difference in findingsbetween the 2 analyses.

Su et al. used a full model approach for covariate selection while thecurrent analysis used step-wise hypothesis testing, with fairlystringent criteria that required achievement of both statisticalsignificance as well as a 5% reduction in IIV. (See Anesth Analg. 2010;110(5):1383-1392.) The data available for covariate assessment alsodiffered from Su et al., where total bypass time was determined to be asignificant covariate as a continuous variable; the current analysis waslimited to evaluation of CPB use as a dichotomous variable indicatingoccurrence or lack of occurrence.

Since no additional covariates were found to be significant, the finalpharmacokinetics model was structurally similar to the base model withthe exception of 2 model refinements consisting of the removal of theallometric exponent on Vc for neonates and simplification of the RVmodel for the Example 1 study to a constant coefficient of variationerror model. The degree of RV was relatively higher in the Example 1study data (46% CV) compared to the Study Example 3 (26% CV) and Example5 data (19% CV). Different levels of enzyme maturation in the subjectsin the Example 1 study are a likely contributing factor to the increasedvariability. In addition, comparatively more data was collected afterlow dexmedetomidine doses in the Example 1 study resulting in anincreased frequency of plasma concentrations in the lower range of theassay where variability tends to be greater.

Overall, all fixed effect parameters were precisely estimated except forthose associated with Q (% SEMs approximately 40%). The estimate of Qwas considerably higher (70.5 L/h) and the unexplained IIV in Q was alsoquite high (163% CV) compared to an initial model based on data fromonly Studies Example 3 and Example 5 (Q=35.9 L/h, IIV in Q=117% CV).This finding may be related to the sparser nature of the data added fromthe Example 1 study and, as a result, the plasma sampling fordexmedetomidine concentrations was less informative to the 2-compartmentmodel parameters in the neonates.

The final pharmacokinetics model for dexmedetomidine was a 2-compartmentmodel as has been previously described in other investigations ofpediatric subjects. Given the remaining slight bias towardsunderprediction of concentrations obtained at later sampling times afterthe end of the maintenance infusion seen in the goodness-of-fit plots(FIGS. 22A-D), a 3-compartment model was also evaluated using theconcentration data from Studies Example 3 and Example 5. However, the3-compartment model fit was essentially identical to the 2-compartmentmodel, and the underprediction bias (FIG. 18) was not corrected. A3-compartment model was not attempted with the addition of the Example 1study data since the sparser data from neonates would be even lessinformative at the later sampling times.

Comparison of fixed effect parameters from the 2-compartment modelpublished by Su et al. (based on only 35 subjects from the Example 5study ranging in age from 1 to 24 months) for a subject aged 7.7 months,weighing 7 kg, and with the median value for total bypass time (57minutes) with those from the final pharmacokinetics model developedherein (based on 115 subjects ranging in age from less than 1 week to 17y) revealed fairly similar estimates, except for Q. Values for CL, Vc,Q, and Vp were 7.26 L/h, 8.4 L, 24.1 L/h, and 10.2 L from the Su et al.model compared to 8.5 L/h, 6.22 L, 68.21 L/h, and 13.21 L from thecurrent analysis. Estimates of the initial distribution (a) and terminalelimination (0) half-lives in the current analysis were 3.2 minutes and1.6 h for a pediatric subject with the median age and weight of 1.56 yand 10.35 kg, respectively, and 7.5 minutes and 1.8 h for a 17 year old,70-kg subject. These results are generally similar to the ranges ofinitial distribution half-life (4.08 minutes to 9 minutes) and terminalelimination half-life (1.6 h to 2.65 h), previously reported fordexmedetomidine given as 1 μg/kg for 5 minutes or 10 minutes, or 0.2μg/kg/h to 0.7 μg/kg/h infusion. (See Diaz et al., Pediatr Crit CareMed. 2007; 8:419-424; Petroz et al., Anesthesiology. 2006;105:1098-1110; and Vilo et al., Br J Anaesthesia. 2008; 100:697-700).

It is also of interest to compare CL and volume of distribution (Vc+Vp)across the age range of the 6 pediatric age groups represented in the 3studies of dexmedetomidine contributing to the pharmacokinetics model(28 weeks to <1 month, 1 month to <6 months, 6 months to <12 months, 12months to <24 months, 2 years to <6 years, and 6 years to <17 years).FIG. 23 and FIG. 24 (upper panels) provide the geometric means and 95%confidence intervals for the individual Bayesian estimates ofdexmedetomidine CL and volume of distribution plotted at the midpoint ofeach age group, with the corresponding weight-adjusted estimates for thepharmacokinetics parameter depicted similarly in the lower panels. Aline for the population model-based typical value of each parameterversus age is overlaid in each plot.

Table 52 and Table 53 provide summary statistics for the individualBayesian parameter estimates and the model-predicted typical valueestimates by age group for dexmedetomidine CL, weight-adjusted CL,volume of distribution, and weight-adjusted volume of distribution,respectively.

TABLE 52 Summary Statistics for the Individual Bayesian Estimates andModel-Predicted Typical Values of Dexmedetomidine Clearance andWeight-Adjusted Clearance by Age Group Weight-Adjusted CL CL (L/h)(L/h/kg) Median Median Predicted Predicted Weight (kg) Age (y) Geo. MeanTypical Geo. Mean Typical Age Group (min, max) (min, max) (95% CI) Value(95% CI) Value 28 weeks  3.12 0.029  2.71 3.04 0.991 0.976 GA-<1 month(1.19, 3.80) (0.008, 0.077) (2.03, 3.61) (0.810, 1.212) (n = 22) 1month-<6  5.99 0.332  6.95 7.56 1.213 1.263 months (3.15, 7.00) (0.099,0.484) (5.52, 8.75) (0.998, 1.475) (n = 14) 6 months-<12  7.28 0.657 8.15 8.75 1.110 1.203 months (5.10, 9.34) (0.521, 0.896) (7.05, 9.43)(0.945, 1.302) (n = 16) 12 months-<24 10.20 1.493 11.34 11.28 1.1181.105 months (8.87, 11.90) (0.973, 1.651) (9.13, 14.07) (0.908, 1.375)(n = 8) 2 y-<6 y 13.75 3.548 15.88 14.11 1.108 1.026 (n = 26) (9.98,23.59) (2.070, 5.761) (14.06, 17.95) (1.000, 1.228) 6 y-<17 y 30.209.887 24.46 25.45 0.796 0.843 (n = 29) (13.60, 99.00) (6.032, 16.967)(19.50, 30.67) (0.695, 0.911)

TABLE 53 Summary Statistics for the Individual Bayesian Estimates andModel-Predicted Typical Values of Dexmedetomidine Volume of Distributionand Weight-Adjusted Volume of Distribution by Age Group Volume ofDistribution Weight-Adjusted V (L) (L/kg) Median Median PredictedPredicted Weight (kg) Age (y) Geo. Mean Typical Geo. Mean Typical AgeGroup (min, max) (min, max) (95% CI) Value (95% CI) Value 28 weeks  3.120.029 15.38 16.90 5.634 5.418 GA-<1 month (1.19, 3.80) (0.008, 0.077)(11.67, 20.28) (4.456, 7.124) (n = 22) 1 month-<6  5.99 0.332 17.2618.91 3.012 3.160 months (3.15, 7.00) (0.099, 0.484) (14.84, 20.07)(2.498, 3.632) (n = 14) 6 months-<12  7.28 0.657 21.27 20.10 2.895 2.763months (5.10, 9.34) (0.521, 0.896) (18.26, 24.77) (2.438, 3.438) (n =16) 12 months-<24 10.20 1.493 25.29 24.23 2.493 2.376 months (8.87,11.90) (0.973, 1.651) (19.84, 32.24) (1.963, 3.167) (n = 8) 2 y-<6 y13.75 3.548 33.51 28.24 2.338 2.054 (n = 26) (9.98, 23.59) (2.070,5.761) (28.94, 38.80) (2.052, 2.665) 6 y-<17 y 30.20 9.887 51.51 53.191.677 1.761 (n = 29) (13.60, 99.00) (6.032, 16.967) (39.84, 66.61)(1.402, 2.005)

In FIG. 23 (upper panel), the steeper slope of the profile exhibited atthe youngest age levels results from the additional maturation covariateeffect on the CL exponent for neonates, with a shallower increase in CLevident with increasing age greater than 1 year. The weight-adjusted CLshown in the lower panel of FIG. 23 also increases between the 2youngest age groups, but then continues to decrease across the remaininggroups. The overall slope of the profile exhibited for volume ofdistribution in the upper panel of FIG. 24 represents the net effect ofincreasing Vc and Vp with increasing weight and decreasing Vp withincreasing age.

Likewise, the pronounced reduction in weight-adjusted volume ofdistribution with increasing age in the youngest age groups (FIG. 24,lower panel) is most likely attributable to the negative effect of ageon Vp (power function), while Vc remains more constant with increasingage. This pediatric pharmacokinetics model can be further used toextrapolate values for pediatric pharmacokinetics parameters to valuesexpected at usual adult ages and weights, for comparison to typicalpharmacokinetics parameter values obtained from the previously developedadult population pharmacokinetics model for dexmedetomidine. Based on ahypothetical pediatric subject at the upper end of the ranges for ageand weight (that is, 17 years and 70 kg), the dexmedetomidine CL andvolume of distribution are predicted to be 47.8 L/h and 114.6 L,compared to corresponding values of 39 L/h (mean body weight associatedwith this CL was 72 kg) and 118 L as reported in the product label forPrecedex.

Similarly, dexmedetomidine CL and volume of distribution were 35.8 L/hand 112.7 L22 in the typical subject from the adult populationpharmacokinetics analysis of long-term (>24 h) dexmedetomidine use, and39.4 L/h and 152 L, respectively, from the noncompartmental analysis ofthis data. These extrapolated results based on a 70-kg subject are alsoconsistent with estimates of CL and volume of distribution standardizedto a 70-kg adult of 42.1 L/h and 125.3 L from a populationpharmacokinetics analysis of pooled data from 4 studies ofdexmedetomidine in pediatric intensive care (subjects aged 1 week to 14years given 1 μg/kg/h to 6 μg/kg/h infusion).24 Overall, this modelprovides a robust characterization of the pharmacokinetics ofdexmedetomidine in pediatrics.

The model evaluation results provide evidence that the model is able topredict well over the entire range of dexmedetomidine concentrationsoccurring during the maintenance infusion, as well as afterdiscontinuation. In addition, this population model is based on thelargest population of pediatric subjects, and broadest range of ages(neonate to 17 years), maintenance doses, and infusion durationsreported to date.

The conclusions of the analysis are as follows. A linear 2-compartmentmodel was found to best characterize the pooled dexmedetomidineconcentration data collected from pediatric subjects enrolled in threestudies after a range of dexmedetomidine doses were administered as ashort intravenous infusion, followed by a maintenance infusion ofvarying duration. •Fixed allometric functions were used to account forthe influence of body weight on all pharmacokinetic parameters in thispediatric population. The allometric exponent for dexmedetomidineclearance was additionally adjusted in neonate subjects. •Theintercompartmental clearance and the volume of the peripheralcompartment for dexmedetomidine were both found to be related tomaturation, as described by age, according to a power function (bothdecrease with increasing age).

The effects of ethnicity, gender, alanine aminotransferase, totalbilirubin, heart physiology (single-versus double-ventricle), use ofconcomitant glucuronidation pathway inhibitors, albumin infusion, use ofcardio-pulmonary bypass, and site of sampling were not identified asstatistically significant predictors of dexmedetomidine pharmacokineticvariability.

Clearance estimates from this model increase with increasing age andweight-adjusted clearance estimates decrease with increasing age,approaching values expected in adults. Volume of distribution estimatesfrom this model increase with increasing age and weight-adjusted volumeof distribution estimates decrease with increasing age, approachingvalues expected in adults. The model evaluation supports the robustnessof the model to predict well over the entire range of concentrations.

Example 7: Pharmacokinetics of Dexmedetomidine in Pediatric PatientsAged 12 Months to 24 Months

A 5-subject, randomized, open-label, single-center study ofdexmedetomidine was conducted on subjects aged 12 months to weeks to <24months of age. The study population consisted of initially intubated andmechanically ventilated pediatric subjects that required sedation in anintensive care setting for a minimum of 6 hours but did not exceed 24hours.

Subjects were randomized into one of two dose levels: dose level 1consisted of a 0.7 g/kg loading dose immediately followed by a 0.5μg/kg/hr maintenance infusion; dose level 2 consisted of a 1 g/kgloading dose immediately followed by a 0.75 g/kg/hr maintenanceinfusion. A total of five subjects were randomized atone site in theUnited States. Two subjects were randomized to dose level 1 and threesubjects to dose level 2. All five subjects who were enrolled in thetrial received dexmedetomidine and completed the treatment. No subjectsprematurely discontinued the study.

The dose levels are outlined in Table 54 below.

TABLE 54 Dosing Levels Loading Dose Maintenance Dose (μg/kg/hr, DoseLevel (μg/kg) as a continuous infusion) 1 0.7 0.5 2 1 0.75

The dexmedetomidine was administered as a 10-minute loading doseinfusion of dexmedetomidine immediately followed by a continuous fixedmaintenance dose infusion of dexmedetomidine across two dose levels sothat the duration of infusion was a minimum of 6 and up to 24 hourspost-operatively (loading dose+maintenance dose combined).Dexmedetomidine was administered at the site of insertion of the IVcatheter to avoid flushing the drug. No other medications were to beadministered through the IV line designated for dexmedetomidine.^(a)

The dexmedetomidine administered was Precedex® (dexmedetomidinehydrochloric acid injection, 100 μg/mL, base). The dexmedetomidinesolution was diluted to 4 μg/mL in 0.9% sodium chloride or dextrose 5%in water. The dexmedetomidine solution was not to be refrigerated.

A subject was allowed to be extubated at any time after dexmedetomidineadministration began. The dexmedetomidine was infused using a controlledinfusion device. Manually controlled microdrippers, macrodrippers, orother nonautomated infusion devices were not permitted. Dexmedetomidinecould not be given as a bolus dose. In order to ensure proper infusion,dexmedetomidine was not administered directly into the pulmonary artery.

The level of sedation was assessed using the University of MichiganSedation Scale. Pain was assessed using the Faces, Legs, Activity, Cryand Consolability (FLACC) scale. Following completion of screeningprocedures, the dexmedetomidine infusion began after discontinuation ofall other sedative agents and after the subject had attained a UMSS ≤4.Sedation dosages were calculated using the subject's most recentlymeasured weight (considered baseline weight).

Subjects who remained intubated or were reintubated during thepost-infusion period or required sedation for other reasons during thepost-infusion period were treated according to standard of care at thestudy site. However, this did not include dexmedetomidine until allpost-infusion pharmacokinetics samples had been obtained. Whenapplicable, open-label dexmedetomidine could resume 24 hours from studydrug discontinuation.

For subjects to be considered evaluable, they must have received atleast 5 hours of continuous dexmedetomidine administration. Thedexmedetomidine infusion could not have extended beyond 24 hours. Oncedexmedetomidine was discontinued (no weaning of dexmedetomidineallowed), post-infusion procedures began and continued for 24 hours.During the dexmedetomidine administration period, the dexmedetomidineinfusion rate could not be titrated.

A schematic of the overall study design is provided below in Table 55below.

TABLE 55 Study Schematic Screening Post-DEX Period DEX Infusion PeriodObservation Period Dose DEX Load DEX Level 1 0.7 μg/kg Maintenance (n =3) 0.5 μg/kg/hr UMSS with rescue MDZ PK sampling FLACC with rescueFentanyl FLACC with rescue Fentanyl Dose DEX Load DEX Level 2 1 μg/kgMaintenance (n = 3) 0.75 μg/kg/hr UMSS with rescue MDZ PK sampling FLACCwith rescue Fentanyl FLACC with rescue Fentanyl 10 minutes 6 to 24 hours24 hours DEX = dexmedetomidine; FLACC = Faces, Legs, Activity, Cry andConsolability; MDZ = midazolam; PK = pharmacokinetic; UMSS = Universityof Michigan Sedation Scale

Adequacy of sedation was assessed using the UMSS throughout the study,with the target level of sedation a UMSS score between 2 and 4. Prior tothe start of dexmedetomidine infusion, a baseline score using the UMSSwas obtained. The UMSS score was measured according to the followingschedule: just prior to loading dose, and then at 5 and 10 minutesduring loading dose; at the start of maintenance of infusion, and at 5,10, 15, 30, and 60 minutes for the first hour; every 4 hours thereafterduring the remainder of the maintenance infusion; and within 5 minutesof obtaining each pharmacokinetics sample.

If a subject was not at the desired target level of sedation (i.e., UMSS<2), rescue medication could be administered for sedation. The rescuemedication was midazolam. Repeated rescue with midazolam (0.05 to 0.1mg/kg) at a recommended frequency of every 2 to 3 minutes per dose or ata frequency based on investigator judgment could be provided until thesubject had reached the desired sedation level. A UMSS was obtainedwithin 5 minutes prior to and within 5 minutes following administrationof rescue midazolam along with the dose of rescue midazolamadministered.

Pain was assessed using the FLACC scale. Rescue opiate analgesia,consisting of IV fentanyl was administered, based on the judgment of theinvestigator, or when the FLACC score was >4. The fentanyl wasadministered either as an intermittent bolus or as a continuous IVinfusion.

If fentanyl was given as a bolus, a FLACC score was recorded within 5minutes prior to and within 5 minutes following fentanyl bolusadministration together along with the dose of rescue fentanyladministered. If fentanyl was given as a continuous infusion, FLACCscores were obtained with the scheduled vital signs every 4 hours. Ifthe infusion was titrated, pain assessments were collected within 5minutes prior to and within 5 minutes following each titration. Therecommended dosage for fentanyl administration was an IV bolus of 1 to 4μg/kg/dose every 2 to 4 hours as needed and a continuous IV infusion of1 to 3 g/kg/hr.

Following the discontinuation of dexmedetomidine, further sedation andanalgesia were allowed to be provided per standard of care; however,dexmedetomidine could not be restarted until after completion of the24-hour post-dexmedetomidine observation period.

Midazolam or fentanyl was used in instances where severeanxiety/agitation or pain was anticipated (e.g., prior to a painfulprocedure, such as suctioning or chest tube removal). The date, time,and type of any painful procedure (e.g., suctioning, chest tube removal)were recorded. In addition, the date and time of any non-pharmacologicintervention (e.g., swaddling, cuddling, and rocking) were documented,and a UMSS and/or FLACC score were recorded within 5 minutes prior toand within 5 minutes following the intervention.

At any time clinically indicated (e.g., subject discomfort despitemaximum doses of rescue), or at the discretion of the investigator, thesubject could have been converted to an alternative sedative oranalgesic therapy that was not permitted within this protocol. This didnot occur in this study.

Thirteen (13) 1 mL venous blood samples (2%2 tsp) were collected via aperipheral venous, central venous, or peripherally-inserted centralcatheter line into heparinized vacuum tubes at each of the followingtime points for pharmacokinetics analysis: no more than 30 minutes priorto start of the loading dose; within 5 minutes before finishing theloading dose; 30 minutes, 1, 2, and 4-6 hours after start of maintenanceinfusion; within 30 minutes prior to end of maintenance infusion (mustbe within 24 hours of start of maintenance infusion); 10 minutes afterend of maintenance infusion; and 30 minutes, 1, 2, 4, and 10 hours afterend of maintenance infusion.

For pharmacokinetics analyses, venous blood samples (1 mL) werecollected in heparinized tubes at a site opposite from the site ofinfusion (e.g., left arm versus right arm). Samples were not drawn fromthe second lumen of a multilumen catheter through which dexmedetomidinewas being administered.

The pharmacodynamics measurements were conducted no more than 5 minutesprior to the scheduled blood draws. Pharmacodynamic measurementsincluded: sedation scores from UMSS; pain scores from FLACC; use ofrescue medication (midazolam or fentanyl); and vital signs, i.e., HR,SBP, DBP, mean arterial pressure, respiratory rate, and oxygensaturation by pulse oximetry.

An adverse event was defined as any untoward medical occurrenceassociated with the use of a drug in humans, whether or not considereddrug-related. An adverse event could therefore be any unfavorable andunintended sign (e.g., an abnormal laboratory finding), symptom, ordisease temporally-associated with the use of a medicinal(investigational) product, whether or not the event was consideredcausally-related to the use of the product.

Such an event can result from use of the drug as stipulated in theprotocol or labeling, from any use of the drug (e.g., off-label, use incombination with another drug) and from any route of administration,formulation, or dose as well as from accidental or intentional overdose,drug abuse, or drug withdrawal. Any worsening of a pre-existingcondition or illness was considered an adverse event. Clinicallysignificant abnormalities were to be followed to resolution (i.e.,become stable, return to normal, return to baseline, or becomeexplainable). Laboratory abnormalities and changes in vital signs wereconsidered adverse events only if they resulted in discontinuation fromthe study, necessitated therapeutic medical intervention, metprotocol-specific criteria, and/or if the Investigator considered themto be adverse events.

An elective surgery/procedure scheduled to occur during the study wasnot considered an adverse event if the surgery/procedure was performedfor a pre-existing condition and the surgery/procedure had been plannedprior to study entry. However, if the pre-existing conditiondeteriorated unexpectedly during the study (i.e., surgery performedearlier than planned), then the deterioration of the condition for whichthe elective surgery/procedure was being done was to be considered anadverse event.

Common post-operative sequelae specifically related to surgery were notreported as adverse events. The following sequelae at the surgical woundsite were considered common surgically-related events and were notreported as adverse events: bleeding, bruising, itching, redness,swelling, numbness, tingling, burning, pain, infection, and wounddehiscence.

For the period immediately following discontinuation of dexmedetomidineand up to 7 days following the start of dexmedetomidine or hospitaldischarge (whichever came first), subjects were followed for the onsetof adverse events. Special attention was made to follow the adverseevents including but not limited to rebound tachycardia or hypertension,signs of withdrawal, agitation/rage, and pulmonary system complications(i.e., acute respiratory distress syndrome). The occurrence ofcomorbidities of prematurity, such as intraventricular hemorrhage,necrotizing enterocolitis, sepsis and persistent ductus arteriosus werealso assessed. No serious adverse events occurred during this study.

All non-serious adverse events that occurred from the start ofdexmedetomidine administration until 7 days following the start ofdexmedetomidine were collected, whether elicited or spontaneouslyreported by the subject. In addition, serious adverse events werecollected from the time the subject's legal representative signed thestudy-specific informed consent form until 7 days following the start ofdexmedetomidine administration.

Laboratory evaluations were drawn at three time points: pre-dose; 4 to 6hours after start of maintenance infusion; and 10 hours after end ofmaintenance infusion. All blood samples were collected in appropriatelylabeled tubes and sent for analysis. Whenever possible, in order toavoid extra blood draws, the laboratory blood samples were drawnsimultaneously with 1 of the scheduled pharmacokinetics samples. Theclinical laboratory tests performed are given in Table 56 below.

TABLE 56 Clinical Laboratory Tests Hematology Blood Chemistry UrinalysisHematocrit Blood Urea Nitrogen (BUN) Specific Hemoglobin Creatininegravity Red blood cell (RBC) count Total bilirubin Ketones White bloodcell (WBC) Serum glutamic-pyruvic pH count transaminase (SGPT/ALT)Protein Neutrophils Serum glutamic-oxaloacetic Blood Bands transaminase(SGOT/AST) Glucose Lymphocytes Alkaline phosphatase Monocytes SodiumBasophils Potassium Eosinophils Magnesium Platelet count (estimateCalcium not acceptable) Phosphorus Uric acid Total protein GlucoseAlbumin

Core body temperature (i.e., tympanic, rectal, or via indwelling device)was monitored. Abnormal body temperatures were to be recorded as adverseevents according to the clinical judgment of the investigator. Subjectswith body temperature fluctuations below 35.6° C. (96° F.) or above38.6° C. (101.5° F.) were evaluated for the presence of an adverseevent.

A physical examination was performed during the screening period toestablish baseline values for evaluations and in close proximity to 24hours after the discontinuation of the dexmedetomidine infusion or onthe day of discharge, whichever came first. All input/output fluidvolumes were captured during the dexmedetomidine infusion period.

Electrocardiograms were obtained at the following times: pre-dose; 4 to6 hours after start of maintenance infusion; and 10 hours after end ofmaintenance infusion. A clinically significant abnormality was groundsfor excluding a subject from entry into the study. All subjectsunderwent continuous cardiac monitoring throughout the dexmedetomidineinfusion period. The interpretation of the ECG was recorded as eithernormal, abnormal not clinically significant, or abnormal clinicallysignificant by the investigator or physician.

Pharmacokinetic assessments of clearance, exposure, distribution, andelimination were appropriate for this study. The pharmacodynamicassessments using the UMSS (sedation) and FLACC (pain) have beenestablished as validated and reliable. The safety measures used in thisstudy were considered standard and suitable.

The primary evaluation was the assessment of dexmedetomidinepharmacokinetics. Data from all fully evaluable subjects (i.e., thosereceiving at least 5 hours of dexmedetomidine infusion) were included inthe analyses. Pharmacodynamic measurements were conducted within 5minutes prior to scheduled blood draws. Standard pharmacokineticsparameters were estimated by non-compartmental methods and/or populationpharmacokinetics methods. Parameters of dexmedetomidine that werecalculated included: area under the concentration-time curve; observedpeak plasma concentration; steady state concentration; plasma clearance;terminal-phase elimination rate constant; observed time to reach maximumplasma concentration, expressed in hours; terminal eliminationhalf-life; volume of distribution; and volume of distribution at steadystate. Additional parameters, including pharmacokinetics parametersadjusted for weight and/or dose may have been determined as deemedappropriate (e.g., plasma clearance, weight adjusted [CL_(w)]).

Pharmacodynamic variables included: sedation scores from UMSS; painscores from FLACC; use of rescue medication (midazolam or fentanyl); andvital signs, i.e., SBP, DBP, MAP, HR, RR, SpO₂.

Analysis of safety variables were based on the incidence of adverseevents, clinical laboratory tests, changes from screening/baseline invital signs, ECGs, and input/output fluid balance. The followingvariables were also assessed: use of rescue regimens to support vitalsigns, use of concomitant medications, and incidence of signs ofwithdrawal (changes in blood pressure or HR) after discontinuingdexmedetomidine infusion.

The statistical analyses were performed using SAS, version 9.1. Forcontinuous variables, N, mean, median, standard deviation (SD), minimum,Q1, Q3, and maximum are presented. The mean and median are displayed to1 decimal place more than the raw value. The SD is displayed to 2decimal places more than the raw value. For categorical variables, N andpercent are shown. All percentages are reported to 1 decimal place.

Descriptive statistics (N, mean, SD, median, min, Q1, Q3, max, and CV[%]) were used to summarize the pharmacokinetics parameters for each ofthe dose groups, and where pharmacokinetically appropriate, across alldose groups. Standard pharmacokinetics parameters were estimated bynon-compartmental methods and/or population pharmacokinetics methods.Normalization of parameters based on administered dose could have beendone as appropriate.

The following pharmacodynamic variables were evaluated: the percentageof subjects that required rescue midazolam for sedation duringdexmedetomidine infusion; the incidence of rescue medication use foranalgesia during dexmedetomidine infusion; the (a) total amount and (b)the weight adjusted total amount (per kg) of rescue medication midazolamor fentanyl given for sedation and analgesia during dexmedetomidineinfusion; the time to first dose of rescue medication for sedation andanalgesia were summarized with Kaplan Meier estimates; the absolute timeand percentage of time on dexmedetomidine infusion that the subject hadUMSS 2-4 and UMSS <2 was summarized for each dose level with descriptivestatistics; descriptive statistics for FLACC scores while on study drugwere summarized using all FLACC scores for a subject; and the time tosuccessful extubation in subjects was summarized with Kaplan-Meierestimates.

The time on dexmedetomidine was summarized descriptively for each doselevel, and also the number and percentage of subjects exposed todexmedetomidine during the treatment period was summarized (N andpercent) by time of exposure for the following time periods (<6 hour,<12 hour, <24 hours) and (>0-<6 hours, ≥6-<12 hours, ≥12-<24 hours, and≥24 hours) by dose level.

Loading dose was summarized using the parameters total dose and durationof dose. Maintenance dose was summarized descriptively for each doselevel and age group by total dose infused (μg/kg), average dose(μg/kg/hr), and duration of hours dosed. Total dose infused equaledinfusion rate (μg/kg/hr) times duration of infusion (hour). The totaldose of dexmedetomidine infused (μg/kg), total dose (μg), and the lengthof infusion (hours) was summarized descriptively by dose level.

Prior and concomitant medications were summarized according to the WHODRUG Dictionary. The number and percentage of subjects who used priormedications (by preferred term) were tabulated for each dose level. Thenumber and percentage of subjects who used concomitant medications weresimilarly tabulated.

Only treatment-emergent adverse events were analyzed. The number andpercentage of subjects with treatment-emergent adverse events wassummarized for each dose level according to the Medical Dictionary forRegulatory Activities (MedDRA) system organ class (SOC) and preferredterm. Category of adverse event severity and category of adverse eventrelationship to dexmedetomidine were similarly summarized. For eachsubject with multiple adverse events, only the most severe category andthe closest relationship to dexmedetomidine were counted once.

Additionally, separate tabulations were created for treatment-emergentserious adverse events, treatment-emergent adverse events leading todiscontinuation, treatment-emergent adverse events related todexmedetomidine, and treatment-emergent adverse events by severity.

For summaries by severity, if a subject had multiple events occurring inthe same SOC or same preferred term, the event with the highest severitywas summarized. Any adverse event with a missing severity was to besummarized as severe. Relationship to dexmedetomidine was summarized asfollows: elated (included definitely related, probably related, andpossibly related) or not related (included probably not related and notrelated).

All laboratory values outside the normal range were flagged in the datalistings and clinically significant abnormal laboratory values wererecorded. The number and percentage of subjects with clinicallysignificant abnormal laboratory values at the baseline, duringdexmedetomidine infusion, and during the post-dexmedetomidine periodwere summarized for each age group overall and by dose level.Descriptive statistics for clinical laboratory tests and change frombaseline were summarized.

The mean, minimum, and maximum of the post-baseline vital signs HR, SBP,DBP, MAP, RR, and SpO₂.measured during the dexmedetomidine infusionperiod and during the 24-hour follow-up were determined for eachsubject. The absolute value and change from baseline was summarizeddescriptively for each of the mean, minimum, and maximum value by doselevel. The incidence of abnormal ECG findings at baseline, duringdexmedetomidine infusion, and during the post-dexmedetomidine period wastabulated by dose level.

The total amount of input (mL) and the total amount of output (mL)measured during the dexmedetomidine infusion period andpost-dexmedetomidine infusion were calculated for each subject, anddescriptively summarized by dose level.

Two subjects received sedatives or analgesics during dexmedetomidineinfusion which were protocol violations. These were two dose level 2subjection, one of whom received morphine and sufentanil for pain andthe other subject received propofol for tracheostomy tube placement.These deviations were not believed to have had an impact on the safetyof the subjects.

The most common medical history included cardiovascular and respiratorydisease in all five subjects. Four of the five subjects hadgastrointestinal conditions. All subjects were post-surgery.

All five subjects received prior medication before entering this studyand concomitant medication during the study. The most common prior orconcomitant drug classes were categorized in the blood and blood formingorgans class (IV fluids and blood products in particular) or drugs forthe nervous system. All subjects received at least onepost-dexmedetomidine infusion medication; the most common drugs were forthe nervous system

The mean plasma pharmacokinetics parameters of dexmedetomidine followinga loading dose and a continuous maintenance dose are given in Table 57below.

TABLE 57 Mean Plasma Pharmacokinetic Parameters Dose Level 1 Dose Level2 DEX LD = 0.7 μg/kg DEX LD = 1 μg/kg MD = 0.5 μg/kg/hr MD = 0.75μg/kg/hr Pharmacokinetic Parameter (N = 2) (N = 3) (units) Mean (% CV)Mean (% CV) CL (L/hr) 12.192 (78.55) 5.836 (50.30) CL_(w) (L/hr/kg)1.292 (87.48) 0.617 (61.79) AUC (0-Infinity) 4639.170 (87.48) 14203.544(91.89) [(pg/mL)hr] AUC (0-Infinity)_(Dose) 118.610 (78.55) 221.131(67.92) [(pg/mL)hr/μg] C_(max) (pg/mL) 4499.925 (129.49) 11737.387(30.24) V_(d) (L) 31.845 (64.17) 15.780 (22.47) V_(dw) (L/kg) 3.343(74.52) 1.590 (39.01) t_(1/2) (hr) 1.958 (19.22) 2.260 (53.99) CV =coefficient of variation; LD = Loading dose; MD = maintenance dosing

T_(max) was generally 0.08 hrs before the end of the loading dose, andwas fairly constant across all subjects and both dose levels. The oneexception (Subject 01-0007, dose level 2) had a T_(max) of 0.68 hrsafter the start of the maintenance infusion.

Exposure to dexmedetomidine, measured as C_(max) or AUC, appeared to bedose-related, although highly variable. Mean C_(max) increased from 4500μg/mL in dose level 1 to 11737 μg/mL in dose level 2, whiledose-adjusted C_(max) was fairly constant. Likewise, AUC (0-Infinity)increased from 4639 (pg/mL)hr in dose level 1 to 14204 (pg/mL)hr in doselevel 2, whereas dose-adjusted AUC (0-Infinity) was fairly constant.This high variability in exposure was mainly attributable to one outlier(Subject 01-0003, dose level 1). Also since dose level 1 and dose level2 contain 2 and 3 subjects, respectively, pharmacokinetics data shouldbe interpreted cautiously (especially in the presence of a possibleoutlier).

Dexmedetomidine half-life was about 2 hrs in all subjects and wasindependent of dose. With the exception of one outlier (Subject 01-0003,dose level 1), both CL and CL_(w) were fairly constant across both doselevels. Clearance was about 5.7 L/hr (2.5 to 8.2 L/hr) whereas weightadjusted CL was about 0.6 L/hr/kg (0.2 to 0.9 L/hr/kg). V_(d) was alsofairly constant across both dose levels. Again with the exclusion of oneoutlier (Subject 01-0003, dose level 1), V_(d) was about 16.2 L (13.4 to19.9 L) whereas weight adjusted V_(d) was about 1.6 L/kg (0.99 to 2.23L/kg).

The mean total amount of midazolam received was 0.50 mg (0.06 mg/kg) inSubject 01-0003 (dose level 1) and 3.70 mg (0.42 mg/kg) in Subject01-0001 (dose level 2) who required rescue midazolam. The mean totalamount of rescue fentanyl received was 60 g (6.62 μg/kg) in 1 subject indose level 1 (Subject 01-0003) and 49.56 g (5.50 μg/kg) in 2 subjects indose level 2 (Subjects 01-0001 and 01-0004).

The mean total amount of midazolam received was 0.50 mg (0.06 mg/kg) inSubject 01-0003 (dose level 1) and 3.70 mg (0.42 mg/kg) in Subject01-0001 (dose level 2) who required rescue midazolam. The mean totalamount of rescue fentanyl received was 60 g (6.62 μg/kg) in 1 subject indose level 1 (Subject 01-0003) and 49.56 g (5.50 μg/kg) in 2 subjects indose level 2 (Subjects 01-0001 and 01-0004).

For dose level 1, Subject 01-0003 required rescue midazolam andfentanyl. This subject required multiple IV boluses of fentanyl for painbeginning 1.43 hours after the start of dexmedetomidine infusion. Thissubject also required one dose of rescue midazolam at 5.27 hours afterthe start of dexmedetomidine infusion for agitation/surgically relatedpain. Relevant ongoing medical history included hypoplastic left heartsyndrome and was post-surgery (cardiac catheterization, left pulmonaryartery stenosis with balloon dilatation and aortopulmonary collateralsthat required coil embolization). The other dose level one subject,Subject 01-0006, did not require rescue midazolam or fentanyl. However,this subject was on lorazepam 1 mg every 6 hours per gastric tube forseizures and could have received chloral hydrate for agitation as neededduring dexmedetomidine infusion. It was determined the subject did notreceive chloral hydrate during dexmedetomidine infusion. This subjectwas post-surgery for a recurrent rectal prolapse with surgical repair.

For dose level 2, Subject 01-0001 required rescue midazolam andfentanyl. Rescue midazolam was given in several doses foragitation/surgically related pain between 1.2 to 5.57 hours after thedexmedetomidine infusion started. Rescue fentanyl was given between 1.62to 6.18 hours after the start of dexmedetomidine infusion for pain inthe form of several boluses and also continuous infusions. This subjectcontinued to receive fentanyl after the dexmedetomidine infusion ended.Relevant medical history included transposition of the great arteries,pulmonary stenosis, and ventricular septal defect and was postoperativefor open heart surgery for correction of these problems (Nikaidohoperation). This subject also received sufentanil IV and IV morphine,both one time each for pain during dexmedetomidine infusion which wereprotocol violations.

Another dose level 2 subject, Subject 01-0004, did not require rescuemidazolam, but did require rescue fentanyl given in the form of severalboluses between 0.67 hours and 5.1 hours after the start ofdexmedetomidine infusion. This subject had a history of congenital heartdisease (congenital defect of the aortopulmonary trunk with trachealcompression and bronchial malacia) and was post-surgery from correctionof these problems (aorotopexy).

The third dose level 2 subject, Subject 01-0007, did not require rescuemidazolam or fentanyl but received propofol during dexmedetomidineinfusion for tracheostomy tube placement (also a protocol violation).This subject had an ongoing medical history of hypoplastic right lungand was tracheostomy/ventilator dependent. The subject had animperforated anus and was post-surgery for colostomy and anorectoplastyand colostomy reversal.

The maintenance infusion doses of dexmedetomidine used in this trial,0.5 μg/kg/hr (dose level 1) and 0.75 μg/kg/hr (dose level 2), weremoderately effective at sedating and keeping subjects comfortable. Theuse of concomitant sedatives and analgesics confounded theinterpretation of the pharmacodynamic results.

Since the subject numbers were so small, the statistical results for thetime to first dose of rescue medication were not statistically orclinically meaningful and are not discussed further.

For rescue midazolam, Subject 01-0003 (dose level 1) received rescuemidazolam at 5.27 hours and Subject 01-0001 (dose level 2) beginning at1.2 hours after the start of dexmedetomidine infusion. For rescuefentanyl, Subject 01-0003 (dose level 1) received rescue fentanylbeginning at 1.43 hours, Subject 01-0001 (dose level 2) beginning at1.62 hours, and Subject 01-0004 (dose level 2) beginning at 0.67 hoursafter the start of dexmedetomidine infusion.

The target UMSS score was between 2 to 4. For dose levels 1 and 2, themedian absolute time spent in this target range was 3.6 hours (58.9% ofthe time) and 5.9 hours (95.1% of the time), respectively. The medianabsolute time spent with a total UMSS score <2 for dose levels 1 and 2was 2.5 hours (41.1% of the time) and 0.3 hours (4.9%), respectively.The results observed are confounded by the receipt of concomitantsedative/analgesic drugs during dexmedetomidine infusion.

One of the criteria used for judging whether to give rescue fentanyl wasif the total FLACC score was >4. The median total FLACC score was 1.6 indose level 1 and 4.4 in dose level 2, and 3.2 for both dose levelscombined. The results observed are confounded by the receipt ofconcomitant sedative/analgesic drugs during dexmedetomidine infusion.Compared to dose level 2 subjects, subjects in dose level 1 spentconsiderably less time in the target UMSS range of 2 to 4, but had lowertotal FLACC scores.

Generally, trends in mean change from baseline in vital signs were notclinically meaningful. There were no treatment-emergent adverse eventspertaining to HR, SBP, DBP, MAP, RR, or SpO₂.

Two of the five subjects were able to be extubated by the end of thestudy. These subjects were Subjects 01-0006 (dose level 1), extubated at17.7 hours from the start time of study drug, and Subject 01-0007 (doselevel 2) extubated at 26.27 hours from the start time of study drug.

The median dose and duration of dexmedetomidine exposure is given inTable 58 below.

TABLE 58 Median Dose and Duration of Dexmedetomidine Exposure Dose Level1 Dose Level 2 Total Median Parameter (N = 2) (N = 3) (N = 5) Loadingdose N 2 3 5 Total loading dose (μg) 7.02 9.11 8.90 Duration (min) 10.010.0 10.0 Maintenance dose N 2 3 5 Total maintenance dose (μg) 30.1141.00 41.00 Duration (min) 360.0 360.0 360.0

Only one of the five subjects (20.0%) experienced treatment-emergentadverse events. These events were mild pyrexia and mild atelectasis in adose level 2 subject; both events were assessed as not related todexmedetomidine. There were no treatment-emergent serious adverse eventsleading to death, no other treatment-emergent serious adverse events,and no treatment-emergent adverse events that led to dexmedetomidinediscontinuation.

There was variability between subjects in hematology tests. In general,no evidence of systematic change for most hematologic variables wasfound. However, subjects in both dose levels had large mean decreases inthe percent of lymphocytes during and post-dexmedetomidineadministration. Subjects in both dose levels had large mean increases inthe percent of neutrophils during and post-dexmedetomidineadministration. Also, dose level 2 subjects had larger mean decreases inplatelets during dexmedetomidine administration compared to baselinethan subjects in dose level 1. Post-dexmedetomidine administration, doselevel 2 subjects had a large mean decrease in platelets while dose level1 subjects had a slight mean increase in platelets.

There was variability between subjects in chemistry tests. In general,no evidence of systematic change for most chemistry variables was found.However, during and post-dexmedetomidine administration, dose level 2subjects had a large mean increase in aspartate aminotransferase (AST)compared to baseline. Both dose levels had large mean increases in uricacid crystals. In general, no evidence of systematic change for theseurinalysis variables was found. No subjects had abnormal hematology,chemistry, or urinalysis results assessed as clinically significantduring or post-dexmedetomidine administration. No abnormal clinicallysignificant ECG findings were present in any of the 5 study subjects atscreening or during or post-dexmedetomidine administration. There wereno treatment-emergent adverse events pertaining to hematology,chemistry, urinalysis results, HR, SBP, DBP, MAP, RR, or SpO₂. The mostcommon abnormal findings at screening and post-dexmedetomidineadministration were in the cardiopulmonary system.

Dexmedetomidine was safe and well tolerated at both dose levels. Themaintenance infusion doses of dexmedetomidine used in this trial, 0.5μg/kg/hr (dose level 1) and 0.75 μg/kg/hr (dose level 2), weremoderately effective at sedating and keeping subjects comfortable.

Example 8: Pooled Pharmacokinetic Data of Dexmedetomidine in PediatricPatients

A population pharmacokinetic evaluation of dexmedetomidine in pediatricsubjects was completed, as described in Example 6. Example 6 combinesthe populations described in Examples 1, 3 and 5. The ages enrolled ineach of the studies were 1 month to <24 months (Example 5), 2 years to<17 years (Example 3) and ≥28 weeks gestational age to <1 month (Example1).

In this study, an additional 11 subjects were included in the modelingdescribed by Example 6. The additional subjects included 6 neonatalsubjects aged ≥28 weeks gestational age to <36 weeks gestational agegroup treated at the second dose level from the additional cohort ofExample 1 (0.1 μg/kg load/0.1 μg/kg/hr Maintenance); and the fivesubjects in the age group 12 months to <24, as described in Example 7.The model parameters were determined as described above in Example 6.Results of the updated model are described in FIGS. 26-33.

Population pharmacokinetic modeling was performed using the nonlinearmixed effects modeling (NONMEM®) computer program, Version 6.0, Level2.0 on an Intel cluster with the Linux operating system.

The first-order conditional estimation (FOCE) with interaction methodwas used at all stages of model development. The effects of both weightand age were included in the model considered the base structural model,given the range of weights and ages in this pediatric population andtheir likely impact on pharmacokinetic. Evaluation of the influence ofother covariates (μgender, ethnicity, cardio-pulmonary bypass use,albumin infusion, and site of sampling on elimination clearance (CL) andvolume of the central compartment (Vc); alanine aminotransferase (ALT),total bilirubin, concomitant glucuronidation pathway inhibitors, andheart physiology (single versus double ventricle) on CL) was performedusing a forward selection (α=0.05 plus at least a 5% reduction ininterindividual variability (IIV) in the parameter of interest) followedby a backward elimination (α=0.001) procedure.

Following any necessary refinements, the adequacy of the final model wasevaluated using a simulation-based prediction-corrected visualpredictive check method. Conditional on the final model point estimates,1000 replicates of the analysis dataset were simulated using NONMEM, andthe 5th, 50th (median), and 95th percentiles of the distributions of thesimulated concentrations were calculated. Prediction correction wasperformed for discrete bins based on the time since the end of theinfusion, treatment group, and age category. Concordance between theprediction interval based on the simulations and the observed data andcorresponding percentiles of the observed data was assessed visually andnumerically, by calculating the percentage of observed data points aboveand below the prediction interval bounds.

The population pharmacokinetic analysis results were as follows. Thebase structural model for the pooled dataset of Example 1, Example 3,and Example 5 was a 2-compartment model with fixed allometric exponentsfor weight effects on clearance and volume parameters (0.75 for CL andinter-compartmental clearance (Q) and 1.0 for Vc and volume of theperipheral compartment (Vp)), an additional shift in the CL and Vcexponents for neonates, and age effects on Q and Vp described by powerfunctions (both decrease with increasing age). (See Example 6).

As a result of forward selection, no additional covariate effects wereadded to the model as none met the pre-specified criteria of astatistically significant reduction in the MVOF and at least a 5%decrease in IIV. During subsequent model refinement, the shift in the Vcallometric exponent for neonates was found to be non-statisticallysignificant and was thus removed from the model.

The final base structural pharmacokinetic model was a 2-compartmentmodel with IIV estimated on CL, Q, Vc, and Vp using exponential errormodels, fixed allometric exponents on the clearance (0.75 for CL and Q)and volume of distribution (1.0 for Vc and Vp) parameters, with anadditional shift on the CL exponent for neonates, age effects on Q andVp described by power functions (both decrease with increasing age),covariance terms for the IIVs on CL and Vp, and the IIVs on Q and Vc,separate additive plus constant coefficient of variation error modelsfor Example 3 and Example 5, and a constant coefficient of variationerror model for Example 1.

The parameter estimates for the final population pharmacokinetic modelfor dexmedetomidine from the original analysis as described in Example 6are provided in Table 51.

All fixed effect parameters were estimated with good precision (% SEMs<20%), with the exception of those associated with Q, which wereestimated with slightly poorer precision (% SEMs of around 40%). Randomeffects were also estimated with good precision (most % SEMs <25%,except IIV in Q with % SEM=37%). Interindividual variability in CL, Vc,and Vp was moderate, ranging from 35% CV to 55% CV. Unexplained IIV in Qwas very high at 163% CV. Overall, RV was the lowest in the Example 5data (around 19% CV) and slightly higher in the Example 3 data (26% CV),but in both studies was considerably larger at low concentration values,especially near the lower limit of the assay. A constant coefficient ofvariation RV model was found to adequately describe the data fromExample 1, with a relatively higher estimate of 46% CV, regardless ofconcentration level.

The prediction-corrected visual predictive check results indicate thatthe model-based simulated concentrations were in close agreement withthe observed data from the 3 studies with 6.3% of observations and 4.7%of observations below and above the bounds of the 90% predictioninterval, respectively. Furthermore, the median of the simulatedconcentration data corresponded consistently with the median of theobserved data.

The additional cohort of Example 1, consisting of six neonatal subjectsin the ≥28 weeks gestational age to <36 weeks gestational age at thesecond dose level (0.1 μg/kg Load/0.1 μg/kg/hr Maintenance), have beencompleted. The five subjects from example 7 for age group 12 months to<24 months have also been completed. These subjects were added to thepopulation pharmacokinetic model described in Example 6, and the modelparameters were determined as described above for the original analysis(i.e., Example 6). There was very little change in the model parametersand the resulting clearance and volume of distribution point estimatesand associated 95% confidence intervals compared to the originalanalysis.

The parameter estimates for the final population pharmacokinetic modelfor dexmedetomidine including the additional 11 subjects completed sincethe original analysis are provided in Table 59.

TABLE 59 Parameter Estimates and Standard Errors From theDexmedetomidine Final Population Pharmacokinetic Model (Studies Example5, Example 3, Example 1, and Example 7) Magnitude of InterindividualFinal Parameter Variability Estimate (% CV) Population % Final %Parameter Mean SEM Estimate SEM CL (L/h)^(a) 10.7 3.4 37.01 17.0Proportional shift in 0.531 17.2 allometric exponent for CL forneonates^(a) Vc (L)^(b) 8.49 10.5 53.76 20.8 Inter-compartmental CL 63.523.8 161.25 23.7 (L/h)^(c) Exponent for power −0.342 27.9 functioneffect of age on Q^(c) Vp (L)^(d) 14.7 7.2 51.19 20.6 Exponent for power−0.280 10.6 function effect of age on Vp^(d) Ratio of additive to 12.315.0 NA NA proportional RV: Example 5 Ratio of additive to 40.4 26.0 NANA proportional RV: Example 3 cov(IIV in CL, IIV in Vp) 0.145 20.8 NA NAcov(IIV in Q, IIV in Vc) 0.796 19.6 NA NA RV Example 1^(e) 0.189 18.6 NANA RV Example 5^(f) 0.0358 16.5 NA NA RV Example 3^(g) 0.0685 20.6 NA NARV Example 7^(h) 0.0935 29.8 NA NA Minimum value of the objectivefunction = 11885.512 Abbreviations: CL, elimination clearance; IIV,interindividual variability; NA, not applicable; NEO, indicator variablefor neonates; % CV, coefficient of variation expressed as a percentage;% SEM, standard error of the mean expressed as a percentage; Q,inter-compartmental clearance; RV, residual variability; Vc, volume ofthe central compartment; Vp, volume of the peripheral compartment; WTKG,weight in kg.${\;^{a}{Typical}\mspace{14mu}{CL}} = {10.7 \times \left( \frac{WTKG}{9.6} \right)^{\lbrack{0.75 \times {({1 + {0.531\; \times {NEO}}})}}\rbrack}}$${\;^{b}{Typical}\mspace{14mu}{Vc}} = {8.49 \times \left( \frac{WTKG}{9.6} \right)}$${\;^{c}{Typical}\mspace{14mu} Q} = {63.5 \times \left( \frac{WTKG}{9.6} \right)^{0.75} \times \left( \frac{age}{1.31} \right)^{- 0.342}}$${\;^{d}{Typical}\mspace{14mu}{Vp}} = {14.7 \times \left( \frac{WTKG}{9.6} \right) \times \left( \frac{age}{1.31} \right)^{- 0.280}}$^(e)Residual variability estimate is expressed as a variance. Thecorresponding % CV for RV in Example 1 is 43% CV. ^(f)Residualvariability estimate is expressed as a variance. The corresponding % CVfor RV in Example 5 ranges from 111% CV at 2.12 ng/L (one-half the lowerassay limit) to 19% CV at 700 ng/L. ^(g)Residual variability estimate isexpressed as a variance. The corresponding % CV for RV in Example 3ranges from 75% CV at 15.12 ng/L (one-half the lower assay limit) to 26%CV at 3000 ng/L. ^(h)Residual variability estimate is expressed as avariance. The corresponding % CV for RV in Example 7 is 31% CV.

Table 60 provides summary statistics for the individual Bayesianparameter estimates and the model-predicted typical value estimates byage group for dexmedetomidine weight-adjusted CL and weight-adjustedvolume of distribution for the original (Example 6) and updatedanalyses.

TABLE 60 Summary Statistics for the Weight-Adjusted Clearance andWeight-Adjusted Volume of Distribution by Age Group Weight-Adjusted CL(L/h/kg) Weight-Adjusted V_(d) (L/kg) Geometric Mean (95% CI asGeometric Mean (95% CI as Percent of Geo. Mean) Percent of Geo. Mean)Including Including Additional 11 Additional 11 Age Group Initial ModelSubjects Initial Model Subjects 28 weeks 0.991 0.929 5.634 5.741 GA-<1month (81.7-122.3) (82.45-121.4) (79.1-126.4) (80.87-123.7) (n = 22) (n= 28) (n = 22) (n = 28) 1 month-<6 1.213 1.211 3.012 3.016 months(82.3-121.6) (82.16-121.7) (82.9-120.6) (82.66-121.0) (n = 14) (n = 14)(n = 14) (n = 14) 6 months-<12 1.110 1.109 2.895 2.893 months(85.1-117.3) (85.21-117.4) (84.2-118.8) (84.17-118.8) (n = 16) (n = 16)(n = 16) (n = 16) 12 months-<24 1.118 1.060 2.493 2.353 months(81.2-123.0) (82.45-121.3) (78.7-127.0) (77.31-129.4) (n = 8) (n = 13)(n = 16) (n = 13) 2 y-<6 y 1.108 1.109 2.338 2.352 (90.3-110.8)(90.17-110.8) (87.8-114.0) (87.63-114.1) (n = 26) (n = 26) (n = 26) (n =26) 6 y-<17 y 0.796 0.796 1.677 1.681 (87.3-114.4) (87.31-114.6)(83.6-119.6) (83.58-119.6) (n = 29) (n = 29) (n = 29) (n = 29)Abbreviations: CI, confidence interval; CL, clearance; GA, gestationalage; Geo., geometric; max, maximum; min, minimum; n, number of subjects;y, years.

Tables 61 and 62 provide summary statistics for the individual Bayesianestimates and model-predicted typical values of dexmedetomidineclearance and weight-adjusted clearance by age group (Table 61) and ofdexmedetomidine clearance and weight-adjusted clearance by age groupestimates by age group for dexmedetomidine volume of distribution andweight-adjusted volume of distribution by age group (Table 62).

TABLE 61 Summary Statistics for the Individual Bayesian Estimates andModel-Predicted Typical Values of Dexmedetomidine Clearance andWeight-Adjusted Clearance by Age Group Weight-Adjusted CL CL (L/h)(L/h/kg) Median Median Predicted Predicted Weight (kg) Age (y) Geo. MeanTypical Geo. Mean Typical Age Group (min, max) (min, max) (95% CI) Value(95% CI) Value 28 weeks  2.89 0.023  2.28 2.69 0.929 0.933 GA-<1 month(1.09, 3.80) (0.005, 0.077) (1.73, 3.02) (0.766, 1.128) (n = 28) 1month-<6  5.99 0.332  6.94 7.51 1.211 1.254 months (3.15, 7.00) (0.099,0.484) (5.50, 8.74) (0.995, 1.474) (n = 14) 6 months-<12  7.28 0.657 8.15 8.69 1.109 1.195 months (5.10, 9.34) (0.521, 0.896) (7.04, 9.42)(0.945, 1.302) (n = 16) 12 months-<24 10.10 1.491 10.76 11.12 1.0601.101 months (8.87, 13.50) (0.973, 1.766) (9.14, 12.67) (0.874, 1.286)(n = 13) 2 y-<6 y 13,75 3.548 15.89 14.01 1.109 1.019 (n = 26) (9.98,23.59) (2.070, 5.761) (14.06, 17.96) (1.000, 1.229) 6 y-<17 y 30.209.887 24.45 25.27 0.796 0.837 (n = 29) (13.60, 99.00) (6.032, 16.967)(19.49, 30.68) (0.695, 0.912) Abbreviations: CI, confidence interval;CL, clearance; GA, gestational age; Geo., geometric; max, maximum; min,minimum; n, number of subjects; y, years

TABLE 62 Summary Statistics for the Individual Bayesian Estimates andModel-Predicted Typical Values of Dexmedetomidine Volume of Distributionand Weight-Adjusted Volume of Distribution by Age Group Volume ofDistribution Weight- Adjusted V (L) (L/kg) Median Median PredictedPredicted Weight (kg) Age (y) Geo. Mean Typical Geo. Mean Typical AgeGroup (min, max) (min, max) (95% CI) Value (95% CI) Value 28 weeks  2.890.023 14.11 16.21 5.741 5.618 GA-<1 month (1.09, 3.80) (0.005, 0.077)(10.95, 18.18) (4.643, 7.100) (n = 28) 1 month-<6  5.99 0.332 17.2818.75 3.016 3.133 months (3.15, 7.00) (0.099, 0.484) (14.83, 20.13)(2.493, 3.649) (n = 14) 6 months-<12  7.28 0.657 21.25 19.95 2.893 2.742months (5.10, 9.34) (0.521, 0.896) (18.23, 24.76) (2.435, 3.436) (n =16) 12 months-<24 10.10 1.491 23.90 23.85 2.353 2.361 months (8.87,13.50) (0.973, 1.766) (18.66, 30.61) (1.819, 3.044) (n = 13) 2 y-<6 y13.75 3.548 33.70 28.09 2.352 2.043 (n = 26) (9.98, 23.59) (2.070,5.761) (29.07, 39.07) (2.061, 2.684) 6 y-<17 y 30.20 9.887 51.65 52.971.681 1.754 (n = 29) (13.60, 99.00) (6.032, 16.967) (39.96, 66.77)(1.405, 2.011) Abbreviations: CI, confidence interval; CL, clearance;GA, gestational age; Geo., geometric; max, maximum; min, minimum; n,number of subjects; y, years

FIG. 26 and FIG. 27 provide the 95% confidence intervals for theindividual Bayesian estimates expressed as the percent of the geometricmean of dexmedetomidine weight-adjusted CL and weight-adjusted volume ofdistribution for each age group as determined from the originalanalysis.

FIG. 28 and FIG. 29 provide the 95% confidence intervals for theindividual Bayesian estimates expressed as the percent of the geometricmean of dexmedetomidine weight-adjusted CL and weight-adjusted volume ofdistribution for each age group as determined from the updated analysis.

FIGS. 30A-H show goodness-of-fit plots for the final populationpharmacokinetic model for dexmedetomidine of the present study. FIGS.31A-B show the prediction-corrected visual predictive check results.Prediction interval overlaid on the observed data is shown in FIG. 31A,and percentiles of the observed data is shown in FIG. 31B. FIG. 32 showsthe geometric means and 95% confidence intervals for the Bayesianestimates of dexmedetomidine clearance and weight-adjusted clearance inspecified age groups with the population model-based typical values ofclearance and weight-adjusted clearance overlaid. FIG. 33 shows thegeometric means and 95% confidence intervals for the Bayesian estimatesof dexmedetomidine volume distribution and weight-adjusted volume ofdistribution in specified age groups, with the population model-basedtypical values of volume of distribution and weight-adjusted volume ofdistribution overlaid.

There was very little difference in the pharmacokinetic model parametersfrom the original analysis and the updated analysis which included theadditional 11 subjects. The final model fully characterizes thepharmacokinetic of dexmedetomidine in pediatric subjects ages 28 weeksGA to <17 years. The results for all age groups from both analyses showthat the 95% confidence intervals are completely contained within 60%and 140% of the point estimate.

The present invention is not to be limited in scope by the specificembodiments described herein. Indeed, various modifications of theinvention in addition to those described herein will become apparent tothose skilled in the art from the foregoing description and theaccompanying figures. Such modifications are intended to fall within thescope of the appended claims.

Patents, patent applications publications product descriptions, andprotocols are cited throughout this application the disclosures of whichare incorporated herein by reference in their entireties for allpurposes.

What is claimed is:
 1. A method of providing sedation in a pediatricpatient in need thereof, wherein the method comprises administering apharmaceutical composition comprising dexmedetomidine or apharmaceutically acceptable salt thereof at a concentration of betweenabout 0.005 to about 50 μg/mL to the pediatric patient; wherein thedexmedetomidine or a pharmaceutically acceptable salt thereof isadministered as a continuous infusion at a concentration of betweenabout 0.005 μg/kg/hr to about 1.5 μg/kg/hr; and wherein the pediatricpatient is less than about 17 years of age.
 2. The method of claim 1,wherein the dexmedetomidine is administered at a concentration ofbetween about 0.005 μg/kg/hr to about 1 μg/kg/hr.
 3. The method of claim2, wherein the dexmedetomidine is administered at a concentration ofabout 0.2 μg/kg/hr.
 4. The method of claim 1, wherein thedexmedetomidine is administered for a period of time of less than about36 hours.
 5. The method of claim 4, wherein the dexmedetomidine isadministered for a period of time of less than about 24 hours.
 6. Themethod of claim 1, wherein the dexmedetomidine is administered by anintravenous infusion.
 7. The method of claim 1, wherein thedexmedetomidine is parenterally administered.
 8. The method of claim 1,wherein the dexmedetomidine is administered to the pediatric patient inan intensive care unit.
 9. The method of claim 1, wherein thepharmaceutical composition comprises dexmedetomidine or apharmaceutically acceptable salt thereof at a concentration of betweenabout 0.005 to about 5 μg/mL.
 10. The method of claim 9, wherein thepharmaceutical composition comprises dexmedetomidine or apharmaceutically acceptable salt thereof at a concentration of about 4μg/mL.
 11. The method of claim 1, wherein the pediatric patient iscritically ill.
 12. The method of claim 1, wherein the pediatric patientis intubated.
 13. The method of claim 12, wherein the pediatric patientis intubated prior to, during, or after administration of thedexmedetomidine.
 14. The method of claim 1, wherein the dexmedetomidineis administered as a single continuous dose.
 15. The method of claim 1,wherein the pediatric patient is less than about 6 years of age.